DURAMAX Diesel Owners

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GMC Chevy DURAMAX Diesels are more "bulletproof" with AMSOIL

Duramax Diesel Owners Page

This extensive page coverage includes:

  • Max protection maintenance for your turbo-diesel Duramax engine, turbocharger, differentials, and transmission.  How to cut wear rates and failures by 50-90%.
  • “Lookup” your specific Duramax truck information, options, recommendations and oil and fluid capacities.
  • Service Interval secrets “beyond the manual”:  BEST options for fluid and oil change mileage.
  • DIESEL POWER CHALLENGE and ULTIMATE CALLOUT CHALLENGE victors: their oils and drivetrain fluids, including the 2014-2017 winner.
  • What 97% of GM’s OEM and dealer staff either don’t understand, or want you to know, about synthetic motor oils and nanofiber filtration technologies, and where AMSOIL and Mobil 1 performance fit in.
  • Diesel Engine Oil CRISIS in the new CK-4/FA-4 SN Service Grades: impact on your Duramax diesel engine oil choice.
  • Duramax Recommendations and options for bypass oil filtration systems.
  • Video of an easy way to take an engine oil sample for analysis.
  • Warranty concerns.
  • Special Duramax Owners Questions and Answers section – our engineers welcome your Duramax questions and give valuable answers.
Look up your Duramax maintenance details






Rear Differential with upgraded aluminum cover - click here for how to prevent diff failure
Your differential should last at least 500k miles. Free Bonus: Click to learn how to prevent diff failure.



How do we know?  We are not marketing people.  We are engineers and gear-heads. This information is your link to experienced Truck Engineers and Lubrication Specialists based out of the auto and truck engineering and manufacturing capital of the world – Detroit, Michigan.  We ARE experts in engines, powertrain, chassis and components, and are passionate about helping you achieve optimum protection, performance and longevity in your Duramax truck.

(Please summarize – which oil should I use?)

You’ve spent your hard earned money on the Duramax Diesel option in one of the most popular and best-designed trucks in the world.  You’re here to maximize the value of your diesel investment, and we’re here to help.  More than ever before with previous GM diesel engines, your Duramax needs an engine oil that delivers the very best wear protection and maximizes engine life.  Your turbocharger needs a great synthetic oil for long life!  Like it or not, 2007+ diesels are saddled with higher EGR levels and DPF systems with regeneration cycles.  But it’s not just the engine.  Torque, horsepower and tow capacity all continue to increase along with operating temperatures, taking your truck’s lubricant stress levels to a point that petroleum lubricants can never handle well.  Duramax truck owners are rapidly realizing the need for high-performance synthetics throughout their drivetrain to maximize fuel economy and enable you to tow confidently, without transmission or differential failures.

What should your oil drain interval be? That depends mostly on the quality and condition of your diesel engine oil and filtration, whose designed performance and protection are factors you can control – by choices you can make.


Ultimate Synthetic Oil presents the Gold Standards in Filtration and Lubrication, with Ultimate Fuel Economy, Wear Protection, Performance, and Environmental Responsibility
AMSOIL Racing with UltimateSyntheticOil.com

Marketing Hype vs Superior Engineered Technology RESULTS


There are no greater demands for balanced performance from street-legal turbodiesel trucks, than three days of competition tests on dyno, 1/4 mile dragstrip, 1/8 mile drag pulling a 10k lb trailer, distance sled-pull, and a 100 mile drive measuring fuel economy.  The Diesel Power Challenge and the Ultimate Callout Challenge trophy winners are the ones that show the best all-around performance. So it’s crucial that these truck’s lubricants deliver balanced performance, exceptionally good in every area. 

From the infancy of the Diesel Power Challenge and the Ultimate Callout Challenge events, the competitors and trophy-winning trucks relied on AMSOIL lubricants throughout most or all of their drivetrains. Many of them didn’t begin their first diesel truck modifications with AMSOIL on board, and they didn’t choose AMSOIL because of sponsorship contracts.  Rather, in their quests for more torque and horsepower without breakdowns, they developed confidence in AMSOIL’s superior technologies for maximum protection and power… and found great fuel economy to be another benefit.  

With year-after-year of all the top competitors using mostly or entirely AMSOIL synthetic lubricants, it just made sense for AMSOIL to become the Official Sponsor of these events.   

Consider Lavon Miller, owner of Firepunk Diesel, who won back-to-back Diesel Power Challenge championships in both 2014 and 2015, then duplicated the feat in 2016 and 2017 in the Ultimate Diesel Callout, and set two Pro Street world records in 2017: Firepunk’s trophy-proud engine, transmission, and front/rear differentials are all protected by AMSOIL synthetic fluids, and Firepunk recommends AMSOIL to all their customers.  Lavon and most top diesel competitors know that AMSOIL not only delivers superior lubrication AND filtration technology that protects even diesel engines with radical levels of torque – AMSOIL also provides the gold standards in synthetic lubricant solutions for all your other drivetrain fluids.

(For a deeper explanation of why we recommend AMSOIL-engineered diesel motor oils for the Duramax engines, review how to pick the best motor oil.)


Don’t let your local dealership service center tell you that you you have to use their brand of oil to “maintain your warranty”.  That is one of the biggest untruths we have heard, yet it goes on day in and day out.  We constantly receive calls from customers that were told this by their servicing dealership. Please be aware that this practice is not authorized or condoned by the auto manufacturers.

For a servicing dealership to essentially tell a customer that they have to use a lower quality oil to “maintain their warranty” is not only wrong but it is also illegal unless they provide it free of charge.  There are Federal laws that protect you against this. But it’s also common-sense: how can using a vastly superior oil, providing the highest levels of protection, void any warranty?  Please read “Vehicle Warranties With AMSOIL” to learn more.

Here’s the bottom line: use of AMSOIL’s REAL SYNTHETIC lubricants throughout the drivetrains of commercial, municipal, and state diesel fleets has multiplied reliability along with fleet service life, maintenance costs go down significantly, and field studies have shown netting an average fuel economy improvement of 6.54 to 8.2%.

Look up your Duramax maintenance details





This new pdf Diesel Power brochure covers important products and information on diesel-powered vehicles like the Duramax.

AMSOIL to the Rescue in the CK-4/FA-3 Diesel Oil Crisis

The pains in the API’s new Service Grades for diesel oil, and why your Duramax diesel engine oil choice is more critical than ever before.

CK-4 Crisis Briefing:  During 2016-2017, the fallout from the pressure of the latest EPA mandates has had a severe and costly impact in diesel engine oils. But most owners are unaware that their engines have been invisibly experiencing high wear rates using approved CK-4 oils.  OEM’s and oil companies have mainly limited explanations of the situation to internal company or industry discussions.  The bottom-line?  Most of the new oils for these Service Grades have failed to provide needed protection levels required for certain internal engine areas.  But worse, while the CK-4/FA-4 oil formulations meet the test requirements, they do not provide adequate protection for older diesel engines: although they were expected (assumed) to be “backward compatible”, they are not.  In response, many OEM’s including Caterpillar, Cummins and Ford have either outright rejected use of CK-4/FA-4 oils, or defined additional unique specifications to test and certify adequate minimum performance levels.  However, the vast majority of dealership and other vehicle service centers, and auto parts stores, are barely aware of these issues – if at all.
What happened in CK-4/FA-3 oil formulations?  It seems that oil producers needed to meet the new service grade requirements on timelines that were too short for the circumstances, being forced to use substantially different oil formulations with completely redesigned additive packages.  In working with formulations well outside their experience and data, most oil producers created formulations for the SAE/API’s brand-new CK-4 / FA-4 specs which appeared to be adequate, yet were later found to be responsible for dramatically accelerated internal engine wear in multiple engine models and brands.

The extreme performance testing that’s embedded in AMSOIL’s engine oil development has once again avoided petroleum-oil industry engine-damage problems, providing dramatically superior protection.  AMSOIL’s completely reformulated lines of diesel engine oils meet or exceed even the most stringent specifications, and are backwards compatible (as noted) to the protection of previous oil service grades including CI-4+ and CJ-4.

(This section has detailed explanations. For a simple summary, see section below: which oil should I use?)

AMSOIL is devoted to protection

Engine Oils Specifically for the DURAMAX Diesel Engines

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For the Duramax engine, AMSOIL has again maxed-out oil protection and performance with three industry-leading, fuel-efficient turbodiesel engine oils.  Through 2016 and into 2017, the oil options split along the model years due to emissions equipment, with 2007 being the wavy dividing line:  early 2007 models followed previous model years because they fortunately lack the Diesel Particulate Filters (DPF’s), and so used “SAE CI-4+” Service Grade oils.  However, by creating new technology formulations, AMSOIL has introduced three new oils to meet/exceed CK-4, CJ-4, CI-4+ and previous Service Grade requirements, AND the additional OEM specifications.

The superior performance of these oils have been firmly established by extensive oil analysis testing and millions of fleet miles. In fact, if you use oil analysis you can usually go much longer on the oil in a year’s time than 2x the OEM drain intervals.  However as a precautionary habit, dipstick checks should always consider any abnormal appearance to the oil, since it can reveal intrusion of coolant or fuel into the oil. Any unusual appearance should be immediately evaluated by a diesel mechanic and/or oil analysis, in order to avoid or minimize engine damage from conditions such as injector or head-gasket failures.

So for 2001 LB7 to 2007 LLY and LBZ Duramax renditions (which all use the 5-speed Allison), all three available oils can be used.  However, the premium performance oil is the new AMSOIL Signature Series Max-Duty Synthetic Diesel Oil 15W-40 (DME).  This is the next-gen technology improvement on the gold-standard AMSOIL “AME” product-code 15W-40 used in many of North America’s semi fleets and as the go-to brute for Diesel Power Challenge contenders.  Max-Duty 15W-40 improves on the overall AME performance to deliver the highest protection and fuel economy, and lowest wear-rates, and is recommended for 2x the GM drain intervals.

The 2007 1/2 to 2010 years which have the LMM Duramax model, and the 2011 to current LML Duramax’s are all paired with the 6-speed Allison transmission and have DPF exhausts.  In order to extend the service intervals of cleaning the DPF filters, the SAE introduced the CJ-4 formulation requirements for engine oils which restricted the important Sulfated Ash and Phosphorus (SAPs) additives and created new formulation/performance challenges for the industry.  The AMSOIL Premium 15W-40 Synthetic Diesel Oil (DME)  and the AMSOIL Synthetic 15W40 OE Diesel Oil (OED) both deliver superior performance that far exceeds the CJ-4 specification for the new 2007+ Duramax engines with DPF’s.  (which oil should I use?)

The first oil (DME) delivers maximum global performance and  protection achievable under SAE CJ-4, together with longer service life.  The second oil (OED) is intended for use at GM’s recommended drain interval, and is formulated with the lower API-marketed formulation restrictions including ZDDP, to equal or outperform any competitive API-Licensed oil on the market.  However, its’ drain interval cannot be extended beyond GM’s recommendations.  When used in conjunction with the AMSOIL Ea nanofiber engine oil filters, the first oil (DME) will deliver lower wear rates and allow you to use oil analysis to extend the oil and filter change interval, and on LML models (2011+) could deliver 1 year or 25,000 miles between oil and filter changes, depending on model year and driving conditions. Otherwise, both of these CJ-4 oils are recommended for use at the longest GM/Chevy oil-drain interval in the manual.  Due to the lower TBN of the low ash CJ-4 formulation, and the driving-habit variability of potential fuel contamination of the oil due to DPF regeneration cycles, longer drain intervals will require oil analysis sampling until more data can be collected on extended drain interval performance.

Other AMSOIL benefits include reduced sludge and deposit formation, extreme temperature protection, improved fuel efficiency and rust and corrosion prevention – and of course it does not void any new vehicle warranty. AMSOIL Synthetic Lubricants meet and exceed all API rated and GM Specifications.  In fact, these lubricants are so advanced that they’ve typically met/exceeded nearly every OEM manufacturer’s published diesel oil test standard, worldwide, without any reformulation.

Q:  Which Duramax engine model years allow the longest drain intervals with AMSOIL’s premium synthetic AME or DME 15W-40 diesel oils?

A: This is an excellent question for owners considering the purchase of a Duramax.  In essence, this question relates to two factors: the use of biodiesel, and the regeneration cycle approach of DPF equipped Duramax vehicles.  These two issues combine in a cumulative way.  Any frequent use of fuel with a B5 (5%) or higher biodiesel component should be considered as mandating oil sampling analysis to extend oil drains out to 20,000 miles or beyond.  B2 is not typically a noteworthy factor in any except the LMM (2007 1/2 to 2010), where it probably does play a small role in further reducing oil life beyond the glaring problem of fuel-contamination of the oil.

The LB7, LLY and LBZ all have an advantage in this question, because none of these 2001 to early 2007 models have DPF’s.  As long as there is no head-gasket or injector leak present (mechanical problems which contaminate the oil), these engines allow AMSOIL AME to deliver 25,000 mile / 1-year oil and nanofiber AMSOIL oil filter changes. Likewise, installation of a BMK-27 bypass filter enables these engines to avoid oil changes by combining filter changes with oil sampling analysis.

The 2007 to 2010 LMM is unfortunately the worst, most risky odds for being able to extend drain intervals beyond the GM recommendations.AMSOIL provides 75% Better Protection 400x300_75ASL

This is because the ACTIVE (not passive) regeneration cycle for the DPF burns out the filter’s accumulation by over-fueling the cylinders (after burn completion) to put diesel fuel into the exhaust, which has the piston rings unavoidably wipe unburned fuel down the cylinder walls into the oil.  Some owners might consider the technical possibility of modifying the exhaust system and engine programming to transition to the superior 2011+ approach (see below).

“Passive” regeneration occurs during normal operation, due to high enough throttle & fuel-burn rates to take the internal DPF temperature above the ~1100°F threshold where the captured diesel fuel particles will be ignited and burned.  “Active” regeneration of the DPF occurs when the exhaust back-pressure builds (diesel particulate matter, DPM, has accumulated enough to obstruct exhaust flow).  To force a DPF burnout, the engine computer sprays fuel into the cylinders at the end of combustion so that the unburned fuel is exhausted into the high-temperature exhaust, raising the DPF temperature high enough to get burnout of the DPM buildup.

Because of the variable of Active Regeneration of the DPF, how the vehicle is used becomes a critical factor in oil contamination for 2007-2010 LMM Duramax’s:

  1. Owners – Managers: Click Here to APPLY FOR AN AMSOIL COMMERCIAL ACCOUNT. Fleet – Facility – Equipment. Get the Best Pricing PLUS Expert Engineering Advice Unfortunately, Duramax “daily driver” 6.6L LMM commuter pickups (2007-2010) in city driving are almost certain to experience a high frequency of active regeneration with oil contamination.  [If a truck will be used in that way and you need to purchase a 2007+ model year, you should instead consider purchasing a 2011+ Duramax-powered vehicle, because the LML engine model changed the active regen approach by adding the Hydrocarbon Injector (HCI) – see below.]
  2. “Foreman use” LMM Duramax trucks are quite likely to experience active regeneration cycles, which can vary from occasional to frequent. Idling and low speeds with light loads will ensure a-regen. In this application, approach extended drain intervals with caution.
  3. Some fleet and “working” LMM Duramax vehicles will experience little or no problem with this fuel contamination of the oil, because they are rarely in active regeneration: these are vehicles which are always adequately loaded and frequently driven in highway traffic with medium to high throttle long enough for the passive regeneration to keep the fuel particulates burned out of the DPF canister.  Caution: OTR drivers should rely on APU’s for stationary power, rather than idling the truck engine during lunch/dinner/sleeping.

The 2011 LML and beyond should be able to deliver extended drain intervals with DME, particularly by adding the AMSOIL BMK-27 dual remote bypass filter kit.  This is because the LML added the Hydrocarbon Injector (HCI), which is simply a 9th fuel injector that sprays fuel into the turbo exhaust down-pipe, eliminating the need to over-fuel the cylinders.  It is now the HCI which injects all the additional diesel fuel into the exhaust stream during active regeneration (cleaning of the diesel particulate filter). This active regeneration strategy is unique to the LML, and will be used for the foreseeable future.  The transition from the late/post injection strategy to the dedicated “9th injector” technique also allowed the LML to receive a B20 biodiesel compatibility rating, which suggests that long oil-drain intervals are even possible with B2 or perhaps B5 fuel.

Q:  What can you expect when changing your Duramax 6.6L to
AMSOIL’s superior synthetic diesel oil?

The commonly recognized changes are the fuel economy bump (~2-5%), lower oil consumption, lower peak engine temperatures under load, and easy cold-weather startups.  For those who already do oil sampling analysis, there’s a substantial decrease in wear-metals, commonly ranging from 30-95%  (direct confirmation of a common 75%+ reduction in overall wear rates). 

One unexpected aspect that can surprise people is oil pressure.  My 2002 Duramax always idled at about 40 psi oil pressure when warm, and pegged somewhere over 80 psi when first started up – when using standard dealer-changed oil.  After the engine flush procedure and change to AMSOIL’s 15W-40 (the same viscosity it always had), the dash oil-gage pressure immediately dropped to about 28 psi warm idle, and about 60-80 psi cold.  That is pretty typical with 15W-40 AMSOIL.  Some people might be alarmed by this lower oil pressure, but it’s a great sign: it means that more oil volume is flowing through a cleaner engine – for better lubrication, better wear protection, better engine cooling – and it’s taking less power (fuel) to pump that oil.


The Secret Power of Nanofiber Bypass Filtration

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BMK27 AMSOIL Dual Remote Bypass Filter Mount for the Duramax
BK309 Dual Bypass Filter Mount in the BMK-27 holds two large filters

The ULTIMATE option for lowest maintenance costs and downtime is to install an AMSOIL Dual Remote By-Pass Filtration System.  This is the highest performance bypass oil filter in the world for light to heavy vehicle applications, and yet it’s also among the lowest cost.  There is a specific kit for the Duramax, the AMSOIL BMK-27 Dual Remote Bypass Filter kit. This bypass filtration system extends the life of the oil in three ways: by adding 1-micron filtration, adding about two more quarts of oil capacity, and adding additional passive cooling for the oil.  With this nanofiber technology system you eliminate over 90% of engine wear, and only change your oil when oil analysis indicates a need – seldom, if ever.  The full flow EaO filter is changed at 15,000 mile (severe service) or 25,000 mile (normal service) intervals and the EaBP Bypass filter is changed at a minimum of 60,000 miles/2 yrs (or longer with oil analysis).

I have over 70,000 miles on the oil change in my diesel Duramax truck [using the AMSOIL Dual Remote Bypass system, which I installed in a few hours with a GM headquarters engineer when we also installed a system on his 2005 Silverado Duramax toy & RV-hauler], and I do oil sampling analysis.  Look here at one of my 6.6L Duramax oil sample reports and you’ll see that I have no TBN or viscosity problem, and wear rates are very low.  And fact is, I probably will never have a problem, even though I’m changing only my oil filters – not my oil.  In this video I used my own Duramax truck to show you how easy it is to pull an engine oil sample for analysis:

See this video on YouTube

Oil analysis can also be valuable without bypass filtration.  When using AMSOIL nanofiber Ea Air and Oil filters, analysis will usually allow extending AMSOIL drain intervals far beyond the guaranteed 15,000 (Severe) or 25,000 mile (Normal Service) drain intervals on non-DPF or on 2011+ LML engines.

Safely Extend Oil Drain Intervals With Zero Warranty Issues:  Download our Free Guide to Oil Analysis Sampling

Need an Oil Analysis Kit or sampling pump?   Visit our Oil Analysis Store

For most gas or pre-2007 diesel vehicle applications using AMSOIL synthetics and nanofiber bypass filtration, oil analysis will show that you NEVER need to change your oil again – even after 500,000 miles!  (This is also likely true of the 2011+ LML engine approach which shifted the DPF burnoff overfueling to be separately injected into the exhaust stream rather than the cylinders.)

How is this possible???  By using highly engineered synthetic oil that is designed to retain its properties and not break down, and using nanofiber filtration that removes all wear particles, (and not over-fueling cylinders so the oil gets contaminated) there is no longer a need to change oil.  The oil is so tough that just topping off the oil level when changing filters is enough to renew the additive package.  This saves a lot of downtime, as well as money, and uses about 80% less motor oil – which benefits both your wallet and the environment.

The AMSOIL Premium 15W-40 Synthetic Diesel Oil (DME) does not break down like conventional petroleum based motor oils, is much more shear-stable and does not have the waxes, paraffins and by-products that come out of crude oil that is pumped from the earth.  Which oil should I use?

The by-pass filter removes the particles that cause wear in your engine down to less than one micron (a micron equals 0.001 mm) and keeps the engine oil analytically clean so you do not need to change your oil for a long time, while still getting far better protection than someone that changes their oil every 3000 miles.  We are experienced at installing these units on Duramax Diesels and can provide you with exact installation instructions, tips, a special custom mounting bracket, and photographs of previous installations.

BMK-27 Installation on 2002 GMC 2500HD Duramax
AMSOIL Dual-Remote Bypass Filter

Over two decades of experience with the bypass filter system shows common results. Laboratory oil chemical analysis every 15-20,000 miles indicates the oil is perfectly suitable for continued service, simply by changing the filters and topping off. Many customers have traveled well over 100,000 miles and oil analysis still indicates no oil change necessary.   My personal Duramax 2500HD CC/SB/4×4 has the bypass system and has traveled 77,000 miles with only filter changes, as of April 2008. (It went on to 120k miles with only filter changes when I sold it.) Here’s one of my 6.6L Duramax oil sample analysis reports, so you can see the data for yourself.

In addition, the AMSOIL By-Pass filter will also remove up to a pint of water from your vehicle’s lubrication system, which is especially important in a diesel engine. Without this the water promotes rust, corrosion and rapid wear. Internal engine heat also creates acids which also wear the engine components. The water and acids build and continue to work destroying your engine even after engine shutdown.

Oil analysis provides a big return for a small investment by: extending equipment life by preventing premature component failure; reducing maintenance costs by eliminating unnecessary component changes and decreasing downtime due to premature scheduled maintenance; enabling calculation of optimum drain intervals that reduce lubricant costs and assure maximum equipment protection.

A regular full flow engine oil filter will only remove wear particles down to the 20-25 micron range, while an AMSOIL full-flow Ea filter removes the majority of particles in the 7-20 micron range with 98.7% first-pass efficiency at 15 microns. But a full-flow filter simply cannot remove all the finer particles because the oil must be filtered quickly while removing most of the particles present in the oil.  That leaves some particles below the 20 micron range. A study completed by Federal Mogul Corp. analyzing over 7000 main and connecting rod bearings concluded that 60% of all engine wear occurs in the 5-20 micron range. This is why no matter how much you change your current full flow oil and filter, regardless of brand, that you still are not removing many of the particles that cause the greatest wear in your engine.

Extensive testing shows that AMSOIL Ea Oil Filters achieve a near-perfect absolute efficiency rating. The exclusive new technology used in AMSOIL EaO Filters provides filtering efficiency to 98.7 percent at 15 microns, and 50 percent at 7 microns. EaO Filters are the most efficient full-flow filters that are available for auto/light trucks, period.

Q: How do EaO filters compare to the full-flow SDF filters that AMSOIL offered for many years?

A: AMSOIL SDF Filters were not as efficient as the modern nanofiber EaO: filtering efficiency was 94.3 percent at 15 microns and 51.2 percent at 7 microns. The AMSOIL SDF full flow filters had a finer synthetic cellulose filtration media, 75% greater efficiency and up to 300% greater capacity than other popular oil filters, as tested according to the Society of Automotive Engineers (SAE) HS806 test method.  They were quite good, but the new Ea filters, with nanofiber technology, are even better.

Now, back to considering the new nanofiber bypass filters, which are used in addition to a full-flow nanofiber filter.  AMSOIL EaBP Filters are high efficiency bypass filters with 98.7% efficiency at two microns. They also remove soot, providing the ultimate in protection against wear, oil degradation and corrosion: your diesel’s dipstick will show remarkably clean oil, darker than from a gasoline engine but not at all jet-black like typical diesel oil.  Most importantly, you virtually eliminate engine wear, because all the wear particles are filtered out of the oil.


Nanofiber AMSOIL Bypass Filter Options
In Center above, the BMK-27 Dual Remote Bypass Filter setup for the Duramax

A complete BMK-27 AMSOIL Dual Remote By-Pass Filtration System kit costs about $500 or less when the Duramax bracket is added (not essential), so it is a very cost-effective improvement that will pay for itself quickly. (Note that the welded-steel Duramax bracket, not shown, is not available from AMSOIL, but through our group by special order. It just makes installation of the system simpler, particularly when installed as typical, below the driver’s floorboard on the inside vertical of the framerail, where the hose length to the adaptor which screws onto the standard Duramax filter location is less than 18″.)

Until you choose to install the Dual Remote by-pass filtration system, the AMSOIL EaO52 full-flow nanofiber engine filter is a significant benefit to the long term durability of your engine, as well as allowing for 25,000 miles of service on the filter.  When you check your oil level every 5,000 miles or 3 months, all you have to do is check the oil level and top it off – don’t drain it or change the filter. (Ignore the OLS Oil Life System – don’t use it, except to remind you to check your oil level.) When you reach 25,000 miles/1-year you can either change the oil and filter or take an oil sample from the dipstick tube using an AMSOIL sampling pump and send it into Oil Analyzer’s Inc using a pre-paid kit. Oil analysis will indicate the exact condition of the oil and whether it is suitable for continued service as well as determining if there are any other engine components or wear items that you need to be concerned with.

For top-quality oil analysis sample kits, tools, and vehicle data trending, Visit our Oil Analysis Store

AMSOIL has a complete line of synthetic oils, greases, transmission fluids, gear lubes, Ea nanofiber air filters, by-pass and full flow filters and bypass filtration systems designed to extend the life of your vehicles and equipment and save you time and money. In addition, for purchasing products at wholesale cost, we also offer a Preferred Customer purchase option, retail sales purchase option or commercial account purchase option for businesses. Finally, we also offer a Dealership Option for anyone interested in becoming an AMSOIL Dealer.
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How to Reduce or Prevent Turbocharger Bearing Seizures on Duramax Diesels

One of the many specific areas, on turbocharged Duramax Diesel engines, that can clearly benefit from the use of synthetic oil is the turbocharger.  When a turbocharged engine is shut off immediately after use, bearing “heat soak” occurs due to the heat that naturally flows up out of the hot exhaust manifold and into the turbo, adding to the high temperatures still present in the turbocharger: all this heat “soaks” into the bearings which are no longer being cooled by a flow of engine oil.  Over a period of time this “cooking” of the residual bearing oil can lead to deposits that can reduce or block the oil flow to the turbocharger bearings, which can lead to turbocharger bearing seizure.

The hotter the outside temperature, the heavier your load, and the less time you allow the truck to idle before shutting off the engine, the greater the risk to your turbocharger’s life.

To combat these problems and give your turbo maximum life, our engineering staff recommend two things: 1) one of AMSOIL’s Synthetic Diesel Oils, and 2) use of a turbo cool-down timer.  A cool-down timer gives your engine a chance to lower the EGT (Exhaust Gas Temperature) to a safer level before the engine shuts off.  A true synthetic oil does not break down and form deposits in the same temperature range as petroleum (“mineral”) oils.  Of these two, the most important is to make sure your Duramax engine oil is a high-quality true synthetic.

AMSOIL’s Synthetic Diesel Oils are inherently far more thermally stable than most diesel oils on the market, and have been shown to keep turbochargers considerably cleaner than other brands of oil. In fact, AMSOIL synthetics have a noted historical reputation for maintaining turbochargers in a clean like-new condition.  Meanwhile, poor quality engine oils have been shown to cause turbocharger bearing seizure in under 100 hours during a “heat soak” test.

Many other engine oils will survive the 100 hour “heat soak” test, but… with considerable deposits and incipient oil passage blocking.  So what oil you select for your Duramax diesel is vital for long turbo life.  If you use typical petroleum name-brand or low-quality diesel oils, it is critical that you let the engine idle for 1 to 20 minutes after use (depending on load, air temperature and driving conditions), to allow the engine and turbocharger to cool. This “cool-down” period does not eliminate deposit formation when using petroleum diesel oils, but it can dramatically reduce it.

The bottom line: To prevent or eliminate turbocharger bearing seizure, there is no substitute for a high quality synthetic diesel oil (like AMSOIL’s) as they have been proven to maintain turbochargers in an almost “as fitted” condition, and significantly reduce deposit formation.  Take a look at the varnish deposits in this picture below, which are the results of a severe high temperature deposit test with some of the most trusted commercial brands. This test clearly shows that AMSOIL keeps engines cleaner longer than other major brands of diesel oils. Which oil would you rather have protecting your Duramax turbo-diesel engine?

Comparative High Temperature Oil Test


Improved Duramax fuel economy savings:

My Duramax diesel truck gained 8% in fuel economy by changing engine oil, gear oil, and transmission fluid to AMSOIL, and my car mpg improved 10% by changing to AMSOIL engine oil and transmission fluid.  While most vehicle owners will only get a 3 to 10% fuel economy improvement with an engine oil change alone, gains of 20% are not unheard of in some vehicles.  Phillip is a customer with a 1999 Oldsmobile Silhouette van who had changed his motor oil at 3,000 mile intervals.  In the spring of 2005 when he used Engine Flush and changed to AMSOIL engine oil with about 85,000 miles on the odometer, he got an instant 20% fuel economy increase which was saving him about $12 per week.  That annual fuel savings of more than $600 is six times more than the $100 annual cost of the AMSOIL products.

In a commercial fleet, changing all drivetrain fluids to AMSOIL usually averages a 5-10% fuel economy improvement.  In rigorously controlled conditions, a small test of commercial Class-8 vehicles got an 8.2% fuel economy improvement by changing all drivetrain fluids to older AMSOIL fluid technologies: now available in historic archives, this was followed up more recently with current products in another test averaging 6.54% improvement.

Improve Your Fuel Economy: the Ultimate Guide




Biodiesel fuels produce more rapid breakdown of ANY engine oil, including synthetics.
No matter what brand or type of engine oil you use, you will need to closely monitor your oil performance with oil analysis and shorten drain intervals as your use of biodiesel blends increases.  B2 fuels are not typically a problem for pre-PDF engines, or for 2011+ HCI-equipped engines, though B5 fuel use needs sampling analysis.  But for 2007-2010 Duramax engine models which over-fuel the cylinders post-combustion to regenerate the DPF, use of bio-diesel will mean cutting your previous oil drain intervals in half (assuming use of the same engine oil).  If extended oil drain intervals are not shortened to near OEM recommendations or at least monitored with oil sampling, biodiesel contamination is likely to produce engine damage due to oil failure.


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Which engine oil should you use in your Duramax Diesel?

To summarize quickly (see Detailed Oil Discussion above), your three choices for 2001 LB7 to 2007 LLY and LBZ Duramax diesels are the 15W-40 AMSOIL Signature Series Max-Duty Synthetic Diesel Oil (product DME, the best maximum-performance option in typical climates), or the AMSOIL Signature Series 0W-40 Max-Duty Synthetic Diesel Oil (DZF) for maximum protection with the best cold-climate performance, or the AMSOIL Synthetic 15W40 Heavy Duty Synthetic Diesel Oil (ADP) for using OEM drain intervals.  For 2007 and later Duramax models which are equipped with the Diesel Particulate Filters (DPF’s), your truck can use either the recommended 5W-40 AMSOIL Signature Series Max-Duty Synthetic Diesel Oil (DME), or either of the other two oils above: all three oils exceed the new CK-4 and the prior CI-4, CJ-4 and earlier specifications.

For optimal vehicle maintenance and cost, UltimateSyntheticOil and DMT Technical do not recommend using ADP unless the only objectives are to gain AMSOIL technology with the lowest per-oil-change cost and OEM drain intervals, and oil sampling will not be used as a Predictive Maintenance (PM) tool.
So any of the three oils will work well for you, and they will all increase your Duramax fuel economy over your current/past oils, but our best engineering recommendation is for you to make an informed choice based on your specific needs and operational priorities.

Here are our summarized suggestions for choosing the best AMSOIL engine oil for your Duramax fleet:

Three Superior AMSOIL Synthetic Diesel Engine Oils
for the DURAMAX – all “Backward Compatible”


Maximum Protection and Performance, with 6X better wear protection at 2x OEM drain intervals*, plus max fuel economy:
       AMSOIL Signature Series Max-Duty             15W-40 (DME)

Maximum Protection in arctic temperatures, for 4X better cold-cranking** performance at 2x OEM drain intervals*:
       AMSOIL Signature Series Max-Duty              0W-40 (DZF)

Exceptional Protection and Performance, with 4X better wear protection at OEM drain intervals, plus improved fuel economy:
      AMSOIL Heavy-Duty Synthetic Diesel Oil    15W-40 (ADP)

(All three meet/exceed CK-4, CJ-4, CI-4+ and previous Service Grade requirements, AND the additional OEM specifications, due to AMSOIL’s superior engineering and commitment to excellence)

*For other than DPF equipped 2007-2010 models or modified engines, or B15 or higher biodiesel percentage fuel, change at 2x OEM service drain intervals, or longer with oil analysis sampling.)

**DZF Pour Point: -48C (-54F). DME PP: -40C (-40F). ADP PP: -38C (-36F)

Ultimate Synthetic Oil Diesel Recommendations


See Duramax Q & A Below

Simply changing your oil more often with “reputable” oil will not give your Duramax all the benefits that AMSOIL offers:

You will not get improved fuel economy, you will not get reduced engine wear, you will not get reduced operating temperatures, you will not get extended drain intervals and you will not save money in the long run.  Please, allow us to show you a better way.  We are here to help you.  You have everything to gain and absolutely nothing to lose!

Recommendations and Related Articles:

Look up your Duramax maintenance details





Duramax Owners Questions and Answers
about lubrication, filtration and other truck maintenance issues:

These e-mailed/posted questions were answered by our degreed automotive engineers.
(None of them are employed by AMSOIL, Inc.)


Q:  What’s the best plan for my whole 2016 Silverado 2500 Duramax drivetrain, to make it last a really long time?

(December 2017 by e-mail)

Brian, I have a 2016 Silverado 2500 Duramax. I removed the OEM exhaust and blocked off the EGR at about 1200 miles. Guessing, I would say I now have about 11,000 miles on the truck. I want this truck to last me for a long time.

I live in AL, just to give you an idea of the weather. I seldom drive the truck. It may sit for 2 months without ever being cranked. It is kept inside an insulated shop-metal building, so temps inside there can probably push 110 degrees during the summer and mid to upper 40’s is the coldest I have seen it.

If driven, it is usually at least 25 miles minimum. I have pulled a few empty goosenecks, about 10k for the heaviest. Those trips are usually 250 miles or more.  So considering it’s deleted, sits for long periods, etc. what oil and other fluids would be your best recommendation?

I like the Bypass-filtration idea, but I had planned on using Puralator PureOne filters.

A:   Johnny, that was EXCELLENT detail on your truck status, use and goals. Here are my recommendations: 

I’ll break this into sections:

FILTRATION – Do what you’d prefer based on your research, of course, but Amsoil’s bypass filtration is 98.7% efficient at 2 microns, and 60% at 1 micron. Check out the BMK-27 system.
If you only use the standard spin-on, the EAO52 filter is designed for 1-yr/25k miles, and the nanofiber media  delivers 98.7% efficiency at 20 microns and is effective down to 15 microns – considerably better than other filters in all aspects.

AMSOIL reformulated the entire diesel oil line to do three primary things: exceed new CK-4+ and additional OEM spec requirements, be ACTUALLY (not theoretically) “backwards-compatible” with previous SAE Service Grades; incorporate the latest additive technologies to retain high performance levels despite the restrictive challenges on additives historically used as best-in-class performance solutions.
What that means is that AMSOIL’s engine oil recommendation is identical for a 2005 Duramax, a 2016 Duramax, or a deleted 2016 Duramax. The AMSOIL Signature-Series Max Duty 15W-40 Synthetic Diesel Oil (product code DME) outperforms any other option. And with a 15k mile Severe Service drain interval recommendation, it’s the most cost effective.

The key reasons why so many Duramax owners install a BMK-27 Dual Remote Bypass Filtration kit:

– Adds ~2 qts oil capacity
– Adds a bit of additional oil cooling.
– Cuts your engine wear rates by more than 90% due to the 2 micron absolute efficiency.
– Zero warranty impact
– EASY transfer to another vehicle if you sell it.
– Ends oil changes in most cases (other than 2007-2010 models with post-burn cylinder fuel injection for active regen cycles), validated by oil analysis: change the full-flow filter annually, and the bypass filter every 2 yrs or 60k miles.
– The savings in oil change cost and in time bring a quick payback for the system, since it’s one of the lowest-cost systems on the market. (~$350 with tax and shipping as a Preferred Customer – see links on UltimateSyntheticOil.comfor that secret to saving ~25% on your purchases.)

DIFFERENTIAL – Your break-in period ended completely between 3-5k miles, and the critical big secret to putting over 1M miles on it without any problem is to change to AMSOIL Severe Gear in 75W-90 or 75W-110 between 5k-30k on the odometer, then change it every 50k-100k depending on use and whether you use an aftermarket Diff Cover.
Change the transfer case fluid on the same interval. You can go to my Vehicle Maintenance page and plug in your truck to get full details and a collection of some valuable tips that are very difficult to find elsewhere. Also, this is a custom link for you that will take you directly to info on YOUR Duramax:

TRANSMISSION – In terms of break-in period and towing, plan this for around 30k miles. If you do a full fluid change, you’re good for 100k miles. If a partial, then use 50k intervals.

FUEL: This has become a very important issue due to degrading fuel quality and properties, and to the many issues of using bio-diesel fuel blends. For you, the fuel issue is particularly relevant for a couple of key reasons: the impact of short-term storage and hot/cold temp cyclic breathing of the fuel tank, and bio-diesel content.  Biodiesel degrades rapidly compared to “fully caffeinated” diesel, with a storage life of weeks rather than months. Degradation accelerates with elevated temps and with cyclic breathing of storage which daily adds more moisture.  So on your link above, be sure to check out AMSOIL’s top technology fuel additives – especially Diesel Fuel Modifier (unless they just modified the name).  This stabilizes the fuel, minimizes microbe growth, adds lubricity for injector and pump life, fights water emulsification separation, and inhibits corrosion.
And when you’re driving, remeber that untreated diesel can form wax crystals starting at 40F and below – Cold Flow Improver is good to keep in mind, particularly filling up in a warm area and driving to a colder one.
I hope this was helpful. If you have other questions don’t hesitate to ask!

Johnny wanted to get deeper, and posed a number of additional questions.  I’ve grouped his questions with our answers:

Filtration –

The BMK27 sounds great!  How much oil is needed for annual testing?​

— I’m not certain but it’s roughly 8 oz in the standard sample bottle.

I assume the petcock is worth purchasing for test samples?

— the sampling approach is mainly preference. More important is being aware of how to do it incorrectly with that technique, and to use the same test method. Pullling the oil sample in a different way or from a different location will often shift the analysis of ppm metals content, and to get effective trending and to understand what “normal” really is for your engine, doing it the same way is valuable. The three most common methods are probably a petcock, an oil sample pump, and filling the bottle from the oil flow while draining the oil pan.

How much does testing cost?

— that depends on approach and what company you use. They are all roughly the same costing, and the slightly more expensive ones tend to have the better reporting/trending reports and online data tools. By “approach” I’m really referring to whether you buy a postage-prepaid sample kit, or a kit where you buy the postage yourself when you mail the kit. That difference drives roughly a $3-5 difference in kit pricing. Fleets normally buy non-postage-paid kits in bulk, to get the volume discount, and to have lower shipping costs by processing through their commercial shipping contract. You can go here to see oil sample kit pricing if you use AMSOIL’s partnering company, Oil Analyzers. To see the pricing difference as a Preferred Customer, put a PC Membership in your cart and the product pricing will immediately change. A key reason many people use Oil Analyzers is because they are intimately aware of the importance of considering test data and trending differently when using AMSOIL products, and their reports are more consumer-friendly than many test labs.

General question, I see the directions say to add oil to filter before installing. Is this the case with normal oil & filter changes? I always install empty.

— Yes, that is always best-practice. That technical wisdom used to be passed along to the consumer at the auto repair shop, over the parts counter, or from dads to sons. You take into account the installation angle of the filter, and fill it “full” based on avoiding pouring oil out when you are installing the filter. There are a few advantages to this, but the easiest one to explain is that you are reducing the amount of time that the engine runs on first startup (after installing the drain plug and refilling with oil) at zero oil pressure, while the oil pump fills the filter. Purists, especially in bygone days with larger filters and previous petroelum oil grades, would then pull the wire boot out of the main distributor coil to prevent firing, or flip a “kill switch”, then crank the engine for 10 or 15 seconds before enabling the ignition again.

Differential – Do you sell a aftermarket cover for both front and rear differentials, and what are prices?

—No, we don’t. There are roughly a half-dozen mfrs that are fairly well known. You can see some picture examples and links on my Stop Differential Failures page, including ATS, PML, Mag-Hytec (the longtime market veteran), and aFe. In general, unless it’s an extreme duty or competition application, people don’t put aftermarket covers on the front differential. If you’re running a triple turbo engine at over 1,000 HP and Ft-lbs torque, in a Diesel Power Challenge or Ultimate Callout Challenge event, then yes, you want a front differential cover. But most truck owners aren’t running 4WD in both sled-pulls and 1/4 mile dragstrip launches at triple the OEM vehicle power, right? (BTW, most of those guys run AMSOIL throughout the drivetrain.) I think the most saavy RV’s or trailer-tow-rig owners use a rear diff cover with a temperature sending port and a viewing sight-glass for oil level verification. The more summer Western U.S. trips and the more power upgrades on the truck, the more important those features become – ESPECIALLY for owners who aren’t running AMSOIL differential gear oil. In applications like that with temperature gauges on the dash, it’s common for owners to note a 15-40 degree drop in peak operating temperatures (i.e. cresting a 15 minute 6% climb) after changing to AMSOIL. I suspect in a fair number of instances, owners value the sight-glass and temp gage as much for the ability to rule out the differential when something “isn’t right”, as for the ability to verify that their differential is running normally.

Transfer case – Recommend changing gear oil if 4wd is never used?

— If you never use it, then I wouldn’t worry about it too much. At least, put on back burner until you’ve got everything else done that you want. For rare use, aside from factors like damage or water intrusion, you should change the front diff fluid to AMSOIL between 50 and 80k, then at 100-150k intervals.

Transmission – Are you saying wait until 30k to change initially?

— Yes… and no… it depends. What were the first 5-10k miles (especially) like on the transmission? It sounds like you’ve done some fairly heavy towing. In that case, if it were mine, I would likely change the fluid anywhere between 10 and 20k miles. If you think that it ran pretty hot, and/or the Allison dipstick is looking suspicious, then change fluid sooner than later. Many people recommend changing the Allison spin-on trans filter every 30k miles (give or take). If you do a full fluid conversion, then you are good with AMSOIL for 50k severe service, or 100k for normal.  In real practice, daily loads/towing in commercial work is severe service.  I consider daily-driver consumer road-use that’s just pulling an RV and/or boat trailer several times a year for a few days or weeks, to be normal duty for a diesel pickup.

Fuel – Based on the attached photo, I run opti-lube now. I hear GM likes Stanadyne. What are your thoughts on them?

— Notice that the testing was done in 2007. The DieselPlace site has nearly 60 pages of forum exchanges on THIS diesel-fuel additives study through 2015, although they began devising and debating a new study in 2013-2015 with another 22 pages of forum discussion… and ended up that they couldn’t fund the study and the additive mfr that offered to do it in their own lab didn’t seem worthwhile for the credibility question in the data. Honestly, I haven’t read most of it, but like nearly all such efforts they are not doing either product research/development work or comprehensive testing: it was only ONE test type, which really doesn’t give the full performance picture of protection level for fuel pumps and injectors. The data doesn’t apply anymore at all because there was very little bio-diesel in 2007, even B-2 provides most of the needed baseline lubricity, and at least MOST of the additves have been reformulated one or more times since. And as they were concluding in 2015, there are a lot of unaddressed questions such as what interactions are there with additives in “normal” fuel instead of fuel obtained to have none of the federally required additive properties.

Overall, I lean to AMSOIL diesel fuel additives for three primary reasons:

A)  The per-use cost is pretty good. Considering the technology/performance level, cost is excellent. But more importantly:

B)  I know that AMSOIL takes an exceptionally rigorous approach to any products they design, to take into account the factors that really count and deliver the best possible performance at a justifiable price. It’s really the trust factor, based on touring AMSOIL facilities, meeting their staff, getting training, and a deep wealth of test-data that’s been backed up by personal and customer experiences. This old-world craftsmanship pride in world-class engineering excellence and stringent production quality controls and lot/batch testing, is VERY different from normal corporate operations today where it’s more about marketing and maximized profit margin than the product quality, performance or value.

C)  In a couple years when better chemistry/technology shows up, or can be leveraged from other AMSOIL products, or when regulations or specifications change, AMSOIL does more development to tweak higher performance, and updates the product formulation with a new maxed-out performance level. In fact, the current Diesel Fuel additives are newly reformulated…

Guess I need to drive my truck more!! Sitting probably does it no good, especially for the diesel fuel.

—That’s probably a good conclusion.

The scary part– How much is all of this total? Disability is now my only income, so I am stuck in a catch 22. I want the best for my truck, hoping to extend its life, but at what cost? Same goes for driving it. I figure letting it sit keeps the miles off, but sitting too much can be bad.

— I wouldn’t worry too much on the costs of converting to AMSOIL.  I had the same concerns when I totaled everything up, but discovered that it all worked to my advantage due to the high value of the AMSOIL performance gains.  Because the conversion is typically spread out like any good vehicle maintenance where you are changing fluids as needed, there isn’t any single big-cost hit. And because everything you change is boosting efficiency, your fuel economy savings are paying for the cost difference in the next AMSOIL fluid changeover.  Many people have tracked the fuel-economy impact and found that their savings are more than the cost of the AMSOIL products: they concluded that AMSOIL’s advantages were not only free but were paying them money to be a smarter consumer.

It’s not typical for someone to have the time and budget to shift their entire vehicle drivetrain over to AMSOIL products. Most people start off with their engine oil, but make a list of what else they need/want to do, and tally up some costs for them, and just plan out each one according to need, time and money. I knew that I wanted to put the Dual Remote Bypass filter kit on my Duramax when I changed over to AMSOIL engine oil, but I couldn’t afford it right then. So I just ran on that oil change for about 6 months and then added the bypass filter kit – I didn’t even change the oil. And the oil sample analysis still looked great ~120k miles later when I sold the truck to fund a cross-country move. In between was only the filter changes and topping the oil back off.

—People don’t usually take interest in “keeping the miles off” a diesel. The great strengths of diesel vehicles are in their load capacity, fuel efficiency, and durable very long life – compared to gasoline engines. It generally takes between 50-150k miles for a diesel engine to actually break in, and the most reliable and easiest indicator of completing break-in is the increase in fuel economy that comes with it… my sense is that 5-15% fuel economy improvements are pretty typical, and 5% is really on the conservative low side.

Best regards,

Brian Dobben – BSMET
Mechanical Engineer, Welding Engineer, Automotive Engineer, Lubrication Specialist
Former Senior Engineer – Chrysler/Dodge/RAM/Jeep/SRT/Fiat headquarters
LeTourneau University Alumni
AMSOIL University Alumni

Q:  Changing All the Drivetrain Fluids in my Duramax truck

(January 2009, Posted on the TruckTrends forum)

I have a GMC Sierra 2500 HD Duramax 4×4 with a 6-speed standard gearbox.  I bought it new in 2001 and now have 98 000 miles on it.  Over the years I always made sure that the maintenance was done as per the owner manual but something bugs me.  Nowhere in the schedule maintenance does it talk about gearbox oil change.  They cover the engine oil, the engine coolant system and all kinds of minor items but they never talk about the standard transmission, the transfer case, the rear and front differentials, and what about the power steering and the hydraulic clutch?  How many years can we go without replacing the oil in all these components?  I understand that they use synthetic oil these days but are these synthetic oils good for the life of the truck?

A:  Recommendations for Changing Transmission Fluid, Transfer Case Lube, and Differential Gear Oil Fluid (Posted by us, 1/12/2009, but we have made a few slight improvements below.)
Become an AMSOIL Preferred Customer to save up to 25 percent, earn points, get exclusive promotions, and win free gear

There’s much more to this subject than meets the eye.  I stumbled across this question today while doing a search, and thought I could help clarify.  I’m a Mechanical Engineer with an ’02 2500HD Duramax, and have spent the last decade in the automotive industry supplying to most of the OEM assembly plants.  I speak fairly regularly with an OEM GM engineer, who also has a Duramax, and we worked together in his shop installing remote bypass filter kits on our Duramax 6.6 engines.  [I later became a Senior Engineer at a Big-3 OEM headquarters, which sadly prompted me to sell my Duramax for the benefit of superior parking, where I sat next to the engineers who were responsible for all the vehicle fluids and lubricants.]

For maximum vehicle life, OEM powertrain engineers (in general vehicle terms, rather than in Owner’s Manuals or Service Manuals) recommend changing ALL lubrication fluids in the first 2,000 to 5,000 miles of service.  This is generally because of the high operating temperatures and high wear-particle content generated during the break-in period, which break down and contaminate the lubricants.  Changing the fluid during this time, instead of at the factory-recommended intervals, can double to quadruple system life. Going to a high quality synthetic will at least double it again (NOT all of them are “factory fill” synthetics, as is often rumored).  For example, the front diff fill cap on 2500HD 4×4’s through some 2004 models are not designed to have long-term compatibility with synthetics, which should tell you something about the factory fluid.  I forget which is which, but one is white, the other black.  You’ll need to order the correct one to go synthetic up front.

It goes back to “planned obsolescence”, which in OEM terms is really just the engineering decisions to hit target goals. Currently, metal finish and surface technologies allow slower wear, so that non-commercial users will make it past warranty with the factory drivetrain fluids, and commercial users will pay for diff and tranny failures that aren’t covered under warranty for commercial use.
You can download a powerfully educational Research White Paper here on Gear Lubes – as far as I’m aware, the most authoritative testing ever published to date (2015), comparing 14 gear oils in 9 important tests:  Gear Lube White Paper

If you note the background info in the first section you’ll start to get a good idea of reality on differential failures, which also translates to tranny and transfer case failures.  Secret: nearly all of them fail, in truth, because their lubricants failed long ago. As as you’ll see in the test data comparing those 14 gear lubes, just because it’s “synthetic” does NOT mean it’s high performance in every important function.

My Duramax purchase was a personally pivotal event because it sparked my shocked research to discover how easy it is to run 500k-1M miles as a 5th wheel tow vehicle… without drivetrain failures (I’m not going to vouch for injectors and fuel pumps, nor for offroading, etc.)  Many truck owners, like myself, plan to keep their trucks for a very long time. If you’re in that group, I recommend that you change everything to true synthetics, and don’t use dealer fluids. Contrary to so many online forum postings around the web, the use of a dramatically superior synthetic lubricant is a dramatically superior choice that does NOT cause failures nor cause the OEM to deny warranty coverage, and the few Dealer service managers who claim otherwise are simply wrong – and wouldn’t dare put their statements in writing.

And beware having a GM dealer change your transmission fluid: I discovered that very few even carry a fluid that meets the Allison TES-295 spec.  Less than a mile from each other, my GM dealer didn’t recommend using a synthetic in the Allison, while the commercial fleet center knew that Allison’s extended commercial warranty required a high-performance synthetic – but still didn’t carry it or use it.  So I negotiated the fluid-exchange fee for bringing my own fluid to the Dealer.  It’s eye-opening for a fleet to learn that Allison’s expensive extended warranty requires the expensive synthetic fluid, but that the fluid itself reduces tranny failures by way over 90%.  Hint – there are only two fluids that meet TES-295, and Allison lists only the non-AMSOIL one that they’re partners with.

(Yeh, unfortunately very few people know this stuff… outside of lubrication, drivetrain, or reliability/maintenance engineers. Any vehicle can be a 500k+ mile vehicle, but it’s just not in the OEM’s or oil-drilling companies’ best financial interests to explain how.  So I expect that this info is very helpful.)

[After the change to AMSOIL’s full synthetic fluids, the transmission, differential, transfer case and power steering synthetic fluids can be changed per AMSOIL’s recommendation based on Normal or Severe use intervals, typically 50k miles severe or 100k miles normal. Fluid analysis may show that 150k mile intervals are acceptable for OTR highway miles.]

Brian – BSMETAMSOIL Preferred Customers save up to 25 percent, earn points, get exclusive promotions, and win free gear
Sierra 2500HD D/A
Diesel Turbo Life Saver
AMSOIL Nanofiber Remote Bypass Filtration and over [120k] miles since last oil change

[p.s. In early 2009, a new report was released which provides some details on a ‘99 Chevy Express 3500 van with the 5.7L gas engine, now over a million miles and still going strong on AMSOIL.  If a spark-plugged Chevy can do that, why not YOUR Duramax?]

Post Comment:

I found your forum post on lubrication to be one of the most useful I have read. I downloaded the white paper you suggested and plan to study it. I am planning to purchase a GMC 2500HD for farm use in several months – to tow tractors and livestock. I have worked as a computer engineer at Sony, Hughes Aircraft and Walt Disney in the past. I would like to read anything you write about your truck or GMC experiences. Thanks for sharing this information! It is really hard to get good facts and reliable sources are so rare. So I really appreciate your efforts.

I have mostly owned Toyotas and had real good luck with them – vehicles and dealers. But the 5.7L Tundra does not have the tow capacity for larger utility tractors with trailer (4 ton and up for just tractor). I once owned the “Ford Explorer from hell” so cannot really imagine going through that run around again – ignition burned out on Mojave desert dirt road after 6 months, shift-on-the-fly did not work consistently the first 2 years until finally Ford installed a new larger spin up motor, door gaskets fell off for no reason, too much to list … and dealing with Ford was an experience not to be believed. After much research the GMC 2500HD with Duramax and Allison trans seems the best choice. But I would love to hear any more thoughts you have on yours.

Ed from Taos, NM


Got a question on your Duramax?
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AMSOIL has been in business since 1972 and was the first company in the world to develop an API (American Petroleum Institute) rated synthetic lubricant for automotive applications. They coined the phrase “extended drain intervals” 40 years ago with 25,000 mile drain intervals, and ever since then they have been defining the leading edge of lubrication technology, innovation and performance.  No other company in the world offers 25,000 and 35,000 mile oil changes, and AMSOIL guarantees their product performance. No-one else does that. AMSOIL is the Gold Standard in lubrication and filtration, and amazingly, their superior-performance products are cheaper to use.  The fact is, if you’re not using AMSOIL lubricants and filters, you’re wasting money.


We are here to help you learn the facts and to show you how using superior AMSOIL products will increase the performance and add to the longevity of your Duramax Diesel, while saving you time and money. Duramax Diesel trucks are excellent vehicles and exceptionally well engineered by General Motors.  In our opinion, they are one of the most advanced diesel vehicles ever produced.  However there are ways to make the performance and longevity even better with AMSOIL Synthetic Lubricants.

(For a deeper explanation of why we recommend AMSOIL-engineered diesel motor oils for the Duramax, review how to pick the best motor oil.)

Skeptical? No problem:

Read our Q&A with hardcore “scamsoil skeptics”

We are here to help, ready to assist you in applying advanced technology lubrication and filtration products for big improvements in your specific applications for any ground or water vehicle or machinery.  We hope you will allow us to show you the proven better ways.  We have many satisfied customers using AMSOIL products in their commercial, trucking, and fleet vehicles, as well as personal, family and recreational vehicles. And now, you know the AMSOIL secret, too.  Welcome to the AMSOIL family!

AMSOIL is the undisputed leader in synthetics………….banner2

Since 1972, AMSOIL Synthetic drivetrain LUBRICANTS have proven to be the highest performance engine oils, greases, transmission fluids, and hydraulic and differential gear oils on the market.
But the other key issue is nanofiber filtration
We cover oil filters, air filters and other fluid filters like NO-ONE else can.  AMSOIL offers the highest performance, most cost-effective, most comprehensive filter line on earth.  Consider air and oil…


Until now, Nanofiber filtration technology has been used exclusively in medical, aerospace, electronics manufacturing, and heavy duty applications, including the US ARMY Abrams M1 tank.   AMSOIL Ea Filters are the first and only filter line to bring this technology to the auto/light truck market.

EaO nanofiber oil filters provide unmatched full-flow filtering efficiency to 98.7 percent at 15 microns, and 50 percent at 7 microns.  This translates to a 70% reduction in engine wear rates, tripling remaining engine life while giving longer filter life and lower pressure drop for better cold-start performance: the only filtration that gives you the best performance in every category!  Compare that to the filters lining the auto-parts shelves, which don’t tell you their common 7,500 mile/6-month design life and either won’t tell you what micron level their efficiency rating is for, or they claim a micron particle size without stating an efficiency: deceptive, meaningless numbers.

Additionally, consider bypass filtration systems for commercial and fleet applications in cars and light, medium and heavy trucks which can filter particles down to less than one micron and are 89% efficient at 1 micron, making oil changes virtually unnecessary and virtually eliminating engine wear.  (A standard full-flow oil filter can only filter to 20 microns with any reasonable efficiency, but 5-25 microns is widely accepted as the wear-particle size range.)  Easy to install, these oil filter systems have been proven by millions of miles of over-the road trucks, construction equipment and fleet service. And we use these on our personal diesel pickup trucks: my Duramax 2500HD had over 120,000 miles since the last oil drain, the oil analysis looked perfect, and the appearance of the AMSOIL diesel oil looks like a gas engine oil with 3,000 miles on the oil.


The MOST IMPORTANT filter on the M1A1 Abrams battle tank is its’ nanofiber air filter.On Patrol Abrams M1A1 Battle Tank beats the dust with Nanofiber Filtration Technology
The MOST Important filter on YOUR vehicle is also the air filter.

It’s far better, and easier, to keep wear particles out of the engine than it is to attempt filtering them out of the engine oil.  Yet filter companies and vehicle manufacturer’s are strangely silent about actual air filter performance and engine needs.  Now AMSOIL offers world-leading breakthrough Ea air filters with exclusive nanofiber technology.  Based on battlefield-proven air-induction systems used in military ground and air vehicles, this high-technology filtration is now available for consumer use!  Ea filters are guaranteed for 4 years, 100,000 miles.  The engineering rule of thumb for damaging wear particle size is 5 to 25 microns.  Incredibly, these filters are 100% efficient at removing particles of 3 microns, and are 80% effective at removing particles of a 1 micron size.  This means that NO WEAR PARTICLES CAN GET PAST OUR Ea AIR FILTERS!  AND, they’re less expensive to use than ANY other air filter.

For Power Sports applications, AMSOIL offers a line of oiled-foam filters.  These filters provide better performance than oiled-gauze air filters, and are used almost exclusively in most off-road applications including baja, dirt-track racing, and motocross.

For light to heavy trucks, both gas and diesel engines, AMSOIL’s partnership with Donaldson provides you with the best performance and most cost-effective air filtration systems in the world.  These include both Powercore and Nanofiber technology filters.  We have the full line of  Donaldson Filters Now Available , including nanofiber air, fuel, water, oil and hydraulic filters, with exclusive performance warranties (no one else in the industry offers filtration performance warranties).  Contact us for specific recommendations, or see our Diesel Page.

Air Induction Systems:AMSOIL EaAU universal conical filters replace filters on custom induction systems made by K&N, Injen, S&B, Green, AIRAID, AFE, TrueFlow and Banks

Well-engineered aftermarket air induction systems can provide airflow improvements with gains in horsepower, fuel economy, and towing torque.  Unfortunately in many cases they may also let far more wear particles into your engine than the OEM filter.  And oiled media can contaminate mass flow air sensors, causing problems with emissions, fuel economy and performance that can even damage transmissions in some cases.  AMSOIL lets you leave those problems behind. The full line of nanofiber universal air induction filters (EaAU) are designed to replace stock oil wetted gauze or foam conical filters that were supplied with custom induction systems produced by K&N, Injen, S&B, Green, AIRAID, AFE, TrueFlow and more. Whether your air induction system is in a gasoline street-rod, or a diesel truck, you have great airflow but you need better filtration and more capacity than you get with oiled gauze or foam.  AMSOIL Ea Air Induction Filters are dry no-oil filters with nanofiber filtration media to bring your aftermarket air-intake far better efficiency, 50 times the capacity, and excellent airflow while being easily cleanable – every 25,000 miles.


  • AMSOIL products saves you time and money.  With recommended extended drain intervals, AMSOIL performance typically costs LESS per year than conventional oil changes.
  • The only 25,000 mile/one-year motor oils in the world.
  • The only 25,000 mile/one-year engine oil filters in the world.
  • A vehicle lubrication solution with far less environmental impact, using an estimated 87% less oil and 5-10% less fuel !
  • The only oils and filters with a warranty for GUARANTEED performance!
  • Exceeds the most stringent performance specifications of all major U.S. and foreign automotive and truck manufacturers.
  • Provides up to four-times the wear protection of other motor oils.
  • Increases the mileage life of your vehicle.
  • Improves fuel economy.
  • Increases at-wheel horsepower.
  • Lowers transmission and differential operating temperatures and delivers better shifting, even in heavy towing.
  • Lowers fleet maintenance costs by lowering the costs of both scheduled maintenance, and mechanical repairs.
  • Lowers fleet capital costs by dramatically extending vehicle service-life.  (Fleet vehicle mileage typically extended 20 to 100%.)
  • Diesel oil and filtration products designed to deliver more than 1,000,000 miles for over-the-road trucks before engine overhaul.
  • Used by many national racing teams, fleets, police departments, fire departments, ambulance fleets, construction firms and trucking companies.



DMT Technical operates UltimateSyntheticOil.com as part of a group of highly skilled team of OEM Engineers and Lubrication and Filtration Specialists.  In fact, we are the ONLY such group on the internet, as well as the largest AND fastest-growing AMSOIL Dealer organization in the nation.   If you have interest in becoming an AMSOIL Dealer , we are skilled at maximizing your efforts in building your own AMSOIL business. Whether as a customer, dealer, or a commercial or retail account, you cannot find a more knowledgeable and skilled group of AMSOIL Dealers anywhere.  That’s because we include former or current OEM headquarters engineers from Ford, Chrysler, and GM.

In addition, as a Dealer in our group you will receive exclusive unlimited product, technical and business support from the only group of Truck and Automotive Engineers and Lubrication Specialists on the net.  That’s priceless – yet free – vital support that can make a huge difference to a growing business.

We possess the skills, desire and knowledge to answer questions, solve problems, improve efficiency, reduce downtime, maintenance costs and increase the durability and life of all of your vehicles.

To get additional information:

If you want to buy AMSOIL Products, visit our vehicle maintenance page, or the AMSOIL On-Line Store or download a clickable pdf e-catalog


AMSOIL is Proudly Made in the U.S.A.

AMSOIL is owned by Americans.

AMSOIL is America’s Oil.

AMSOIL United States and Canada the Filtration and Lubrication Gold Standards

Brian Dobben - former Senior OEM Engineer, USA and Canada Amsoil Synthetic Oil dealer - premium oils and filters

Ultimate Synthetic Oil – AMSOIL Products

Garner, North Carolina  27529

Phone: (419) 551-4792


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