How to Guard Against Ethanol’s Downside in Fuel

Don’t Ignore Ethanol’s Destructive Potential

Ethanol added to gasoline has long been marketed as if it is all-good, win-win.  But ethanol is a bit controversial because it has a destructive side that can really bite your wallet if you don’t guard against it.  Lets talk about the negative effects that ethanol can have on fuel-system components, especially in powersports and lawn & garden equipment – and what you can do to avoid those problems. But first, some background info.

What is ethanol?

Ethanol is an alcohol fuel derived from plant materials, such as corn, barley or wheat. It’s mixed with gasoline at different ratios to produce the fuel you buy at the pump. Most people see E10 at the pump, which is gasoline that contains up to 10 percent ethanol. Today, E15 is becoming more common. And owners of flex-fuel vehicles designed to run on increased concentrations of ethanol can opt for E85.

The upside of ethanol

Years ago, lead was added to gasoline to, among other things, boost octane rating and help prevent engine knock. It turned out lead poisoned catalytic converters and harmed the environment, so it was replaced by methyl tert-butyl ether (MTBE). However, MTBE was shown to damage the environment if leaked or spilled. Today, ethanol has replaced MTBE as a more environmentally friendly means of boosting octane.

Fuel-system problems

That brings us to a major knock on ethanol – it’s propensity to degrade rubber and plastic fuel hoses and carburetor components. Ethanol can cause gaskets and fuel lines to harden, crack and then leak. It can also cause aluminum and brass fuel-system components to corrode and develop a white, flaky residue that clogs fuel passages.  The problems are extensive, widespread and costly in marine, powersports, and lawn care equipment.

Some marina personnel say that up to 65 percent of their repair orders are attributed to fuel-system problems.  Some lawn equipment professionals even recommend that:

  1. You should never buy used lawn equipment unless it is very cheap, because much of what’s sold has serious internal fuel-system problems that need repair.
  2. You should find a source for 100% petroleum gasoline, and use pure gasoline for all of your powersports, marine and other seasonal equipment.

Beware!  NEVER put E85 (85% Ethanol, 15% gasoline) into a vehicle that is not FLEX-FUEL and stated clearly by the OEM to be designed to permit use of E85.  Putting E85 into non-flex-fuel vehicles WILL cause damage that shortens the life of fuel system and engine components.

Ethanol isn’t to blame

Phase Separation in Ethanol Gas Fuels like E15

While ethanol has become a popular scapegoat for mechanics, especially in the marine industry, it isn’t the enemy – time is the enemy.

Why do ethanol related problems affect powersports and lawn & garden equipment more than your car or truck?  It’s because your boat or lawnmower can sit idle for weeks or even months. During that time, the fuel can absorb moisture since ethanol has an affinity for water. The more moisture available, and the more the fuel tank “breathes” in heating/cooling cycles (daytime/nighttime temperature changes), the faster it pulls water into the fuel.  That’s why ethanol related problems are so common and magnified in marine applications: as the fuel sits unused in the tank through daily heating/cooling cycles, the high humidity accelerates water absorption and fuel breakdown.

So why is this bad?  Water can break the molecular bond between gasoline and ethanol, causing the water/ethanol mixture to separate from the gasoline and fall to the bottom of the tank. This is known as phase separation, and you can see an example of it in the image above, with gasoline on top of ethanol and water on the bottom.

Phase separation causes several big problems. The engine can draw the ethanol/ water mixture into the carburetor or injectors, which accelerates injector-wear and also creates a lean-burn situation that can increase heat and damage the engine. In addition, the gasoline left behind no longer offers adequate resistance to engine knock since the ethanol that provides the increased octane the engine needs has separated from the gasoline. Burning low-octane gas can cause damage due to engine knock, especially in two-stroke engines.

Finally, if your boat, lawnmower or other piece of equipment sits unused, the water/ethanol mixture can slowly corrode aluminum and brass fuel-system components, not to mention rubber and plastic fuel lines and gaskets.  Since water is the lowest separation layer, it lays directly on the bottom of storage tanks and in the low points of fuel piping: where those tanks or pipes are steel, they will corrode, and where they are plastic they will degrade.  Eventually those components fail and require replacement, and it can happen with surprising speed.  That’s one reason why boats are required to use components made of USCG approved materials.

Driving your car or truck almost every day doesn’t allow enough time for phase separation to occur, which is why we don’t see these issues nearly as often in the passenger car/light-truck market.  But in outboard motors, weed-cutters, motorcycles, jet-skis and other seasonal equipment, the problems are huge.

While it’s true that OEM manufacturers can change designs to reduce deterioration in these weak spots, it’s often much easier said than done.  In fact it can take several years to achieve reasonable reliability and life.  And those design changes do nothing to reduce problems in older-design equipment.

Prevention is the best solution

Although some fuel additives on the market claim to reverse the effects of phase separation, there’s no way to reintegrate gasoline and ethanol once they’ve separated. Instead, it’s best to prevent it. Here are the main ways to avoid it:

  1. The best solution is to use non-oxygenated, ethanol-free gas in your powersports and lawn & garden equipment. It costs a little more, but using 100% gasoline eliminates the problems associated with ethanol.  Unfortunately, it’s become hard to find “straight” gasoline.  Otherwise, use the lowest Ethanol content you can find, such as E5 or E10.
  2. Eliminate or control the gas-tank “breathing”:
    – Use climate-controlled storage, which virtually eliminates the “breathing cycles” of the fuel tank, and reduces the air humidity.
    – Keep the gasoline tank in shade.
    – Keep the gas tank full.  Fill up when you are done using the equipment for that day or week:  that minimizes the volume of “breathing air” that the tank can pull in/out with the daily temperature swings.
  3. At the end of the season, or whenever it will be sitting idle for months, treat the gasoline and drain and purge the fuel system.

In most cases these approaches are impractical, inconvenient and sometimes unsafe.  But fortunately there is another, more practical solution: treat every tank of fuel and container of gas with AMSOIL Quickshot ®.  It helps keep water molecules dispersed in the fuel to prevent phase separation. It also cleans varnish, gums and insoluble debris while stabilizing fuel during short-term storage.  Quickshot is highly engineered to help you avoid ethanol-related problems and keep your equipment protected.  There’s nothing controversial about guarding your equipment and your wallet.

Written by:  Len Groom with Brian Dobben.
Len is a Technical Product Manager with AMSOIL.
Brian is a former OEM headquarters Senior Engineer with over two decades experience in automotive engineering, and he is an AMSOIL Dealer who started out of his passion to educate people on the huge advantages of AMSOIL’s globally-recognized engineered expertise in automotive lubrication, filtration and service fluids. 

Fuel Contamination with DPF Systems

 DPF-Burdened Diesel Engines Are Fighting a Fuel-Contaminated-Oil Battle and LOSING !

It’s Time to Armor-Up Your Turbodiesel with AMSOIL.

Chart of Synthetic Diesel Oil Viscosity Performance at 4% Fuel Dilution

At 4% fuel dilution, AMSOIL delivered. The competition failed.

Diesel fuel is a natural solvent, and quickly reduces the motor oil’s life expectancy and effectiveness.  In diesel engine oil, a fuel dilution rate of 2 percent is abnormal and anything over 5 percent is excessive.  Fuel dilution leads to reduced oil viscosity, reduced oil film strength, increased engine wear (particularly in the cylinder/ring area), increased volatility, weakened lubricant detergency, accelerated lubricant oxidation, varnish formation, acid formation/corrosion and low oil pressure.

Factors such as frequent starts, excessive idling, short trips and cold starts have contributed to moderate levels of fuel dilution in diesel applications for years. But recent issues created by modern Diesel Particulate Filters (DPF’s) and other emissions management strategies have brought the fuel dilution problem to a whole new level.  For example, increasing fuel dilution levels are documented in 2007+ Caterpillar C13 and C15 on-highway engines.

In addition, the DPF regeneration process in 2007 to present GM, Ford and Dodge diesel pickups has also been identified as a major cause of troubling levels of fuel dilution.  Except for the 2011+ LML Duramax engines, all 2007+ OEM engines employ an “active” regeneration strategy that includes in-cylinder injection of raw diesel fuel during the piston’s exhaust stroke.  Some of the fuel is wiped/washed past the rings and directly into the crankcase, diluting the oil.  This periodic washing of raw fuel into the oil makes it even more prone to viscosity loss and places the engine at greater risk of abnormal wear.

AMSOIL’s premium CJ-4 Synthetic Diesel Oils stay within viscosity grade, even when diluted with 4% fuel – which has now become common in some vehicle conditions. Even though no oil can provide a decrease in your oil-dilution rates from regeneration over-fueling, AMSOIL CAN and DID provide superior protection for higher levels of fuel dilution than was previously encountered in normal diesel engine operation.  AMSOIL’s engineers understand the huge negative impact of fuel dilution problems on engine longevity due to DPF active-regeneration (as noted in the leading paragraph), so they made sure that AMSOIL’s diesel oils continue to maintain viscosity and other essential properties at higher fuel dilution rates, long after other oils have failed.

What oil’s in YOUR turbodiesel engine?  Here’s how to pick the best engine oil(opens in new tab)

(Published in 2009, the G2752 test report was archived due to one or more oils being reformulated, so that the performance results may have become inaccurate for revised formulations. However, the DPF active-regen fuel-in-oil problem is very real in diesel engines, especially when the truck is primarily a non-loaded commuter or idles extensively.  The report still illustrates AMSOIL’s history of superior lubricant engineering that provides a much wider margin of performance above minimum OEM requirements, which deliver valuable advantages under unexpectedly adverse conditions, preserving the life of your engine, transmission, differential.  Click link to open full G2752 test report in a new tab.)

(Brian Dobben – former OEM Headquarters Senior Engineer)

For detailed model-specific info on DPF engine oil fuel contamination, and other insider engineering tips for Dodge RAM, Ford, GMC and Chevrolet turbodiesel pickups…


DODGE RAM Cummins Diesel Owners Page
Ford PowerStroke Diesel Owners Page
Duramax Diesel Owners Page

UltimateSyntheticOil promotes the AMSOIL Filtration and Lubrication Gold Standards in the United States and Canada 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

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