HOW TO IMPROVE YOUR FUEL ECONOMY –
The Ultimate Fuel Economy Guide:
Looking for the best overall FREE information on getting the most Miles Per Gallon (maximum MPG) with any vehicle? You’ve finally found it!
Whether you need to save fuel in your RV, car or truck, it’s covered right here.
Our lead engineer (a former Senior Engineer at an OEM headquarters) lists more than 80 different ideas here to improve fuel economy. So if you don’t find a new idea or information to save you money, you’re a rare exception.
This guide is “complete” but still being improved: If you have additional suggestions, please let us know. E-mail to .
Fuel prices will rise again and set new all-time record highs. Many sources offer helpful tips to increase fuel economy. But most are incomplete and lack important details that can save you big money. Surprisingly, most of them overlook at least two of the easiest changes you can make to produce big improvements in your MPG!
That’s why we’ve worked hard at UltimateSyntheticOil.com to create the most complete Ultimate resource available: to help you save fuel in your car, truck, RV, boat, motorcycle, or fleet.
Tips are covered in two major categories – driving habits, and vehicle maintenance/repair/upgrades (including aftermarket parts). There’s a lot of information here which we have improved more than 17 times (current Revision # and date are posted at the bottom of this article). BookMark this page and forward a link!
First, DRIVING HABITS:
- Anticipate, coast, and use your brakes less. Look far down the road ahead, even if “far” means half a city block. Get into position for turn-lanes smoothly and early so that you don’t have to accelerate to get in front of traffic. Anticipate stops or slow-downs ahead and take your foot off the gas: try to coast much more than you brake. Keeping more distance to the car in front of you will help.
See a long train at the RR crossing ahead? Get your foot off the gas immediately. You can idle forward in Drive for a long way (without braking), for ~30% less fuel than sitting in Drive, and nearly the same fuel use as sitting in Park.
Remember: any additional distance you coast will save fuel and extend your brake-pad life.
- Don’t accelerate quickly. Remember that the guy who leaves the stoplight the quickest also pays more at the pump. Accelerating at about 1/4 to 1/3 throttle may be slower than you’re used to, but it saves a lot of fuel. Whether you’re driving an automatic or manual, this will tend to shift up to higher gears at slower speeds, turning fewer engine revolutions.
- Minimize idling, and idle smart: Engines only need 10 to 30 seconds for warm-up, and idling your engine for more than a minute typically costs more fuel than re-starting it. So avoid the drive-thru lines at the bank and the fast-food shop: instead of sitting in line, park and go inside. BUT, when you must idle with an automatic transmission, put the transmission in Neutral or Park while you’re waiting: this will cut your fuel usage at idle by 10-35% depending on the vehicle.
If you have a manual transmission, don’t use the clutch to keep from rolling back – use the brake. That saves fuel and extends your clutch life.
- Use Cruise Control. It’s proven to save fuel. But it’s not just for highway cruising. Using the “Resume” button on your cruise control can be a handy compromise to provide reasonable acceleration that doesn’t irritate drivers behind you, without wasting fuel.
- Overdrive and gear selection. If you have an automatic with Overdrive, use the Overdrive. If you have a manual transmission, shift early to keep engine rpm’s lower and be sure to use the highest gear for highway cruising.
- Slow down. As you increase speed above 60 mph, wind resistance starts increasing your fuel consumption. Estimates are that every mile over 60 mph costs you 1% in fuel economy. In other words, when you speed, you’re paying more at the gas pump.
- Watch your tire choice. Replacing your tires/wheels with wider and/or taller ones may look awesome, but keep in mind that your choice could have a 1 to 3% penalty in fuel economy… or even more in extreme cases like “monster truck” tires/wheels.
- Carefully consider your route and the time of day: traffic flow is a huge factor.
For example, see the picture to the right. Those vehicle-following-distances are typical of traffic in many large cities. If this highway traffic is stop-and-go, fuel economy will be bad. On the other extreme, if the traffic is moving smoothly and fast (at 60 – 80 mph), then your fuel economy is going to be superb: those rushing vehicles create a jet-stream of air which dramatically reduces your wind-drag losses – 10 to 30% improvements are possible. For maximum fuel economy, follow a larger vehicle and use your cruise control (just bump speed up/down 1 mph to adjust). Also, keep in mind the wind direction: if there’s a strong wind blowing in from the right, and you drive in the right lane, you get no break in wind resistance. In that case, move over one lane to the left in order to keep a wind-drag advantage.
- Plan and Combine errands to make fewer trips. Think like your great-grandparents did. Plan meals and grocery shop once a week or twice a month; just make a list of other errands during the week, plan your route, and do it all on the same day. Dropping off the kids at practice? Arrange with other parents to carpool or to pick them up for you.
Such planning may seem like work at first, but it will give you more free time, help you relax, and can improve your average fuel economy by 5 to 15%. It can also cut your average weekly mileage by 20% or more. Total dollar potential: save 10-35% of monthly fuel costs.
How does this help fuel economy? During the first several miles while warming up, the engine and transmission are not operating at full efficiency. This is why city fuel economy can drop dramatically in cold weather, when it can take 10 miles for the transmission to warm up. Automatic transmissions in particular can be huge power hogs when fluid is cold (hot/cold temperatures are one of many reasons to use a full-synthetic 100,000-mile transmission fluid – see more on this below), and manual transmissions can feel like you’re shifting in molasses. So, combining two or three trips into one will not only reduce the miles you drive, but will get you better fuel economy on the way.
- Drive first to your furthest destination of the day. When running errands, driving to your farthest point first will warm up your vehicle’s engine and transmission most quickly, which allows it to operate with more efficiency during the rest of your stops.
- Clear off the snow and ice. Snow and ice buildup costs you fuel in two important ways: it increases your vehicle’s wind resistance, and it adds a lot of weight.
- Use an engine block heater in winter. When your engine warms up more quickly, it gets efficient more quickly. But “idling” your engine is an expensive way to warm it up in the winter. Instead, have an engine block heater installed and plug it into a hardware-store timer. Depending on the engine temperature, 1 to 3 hours on the timer will give you an optimal boost for your fuel economy.
- Use air conditioning wisely. In city driving at 35 mph or less, it’s cheaper to use the vents and/or roll the windows down. But at highway speeds, it’s a different story: rolling the windows down will cost you more fuel than using the air conditioner. In addition, you might shut off the A/C a couple of minutes before you get to your destination. These factors can affect fuel economy by ~ 1-3%.
- Drive in style – tint your windows. Window tinting offers both privacy and “coolness”, by reducing the load on your Air Conditioner. It also extends the life of your interior by lowering the interior’s temperature when sitting in full sun, as well as by blocking UV rays. Just be careful to select tinting that isn’t darker than what’s legally allowed in your state.
- Close passenger air vents. If your vehicle is a commuter rather than a family car, you don’t need to be cooling your entire car interior – just you.
- Buy fuel wisely. Ok, this isn’t actually improving your fuel economy, but there are several things to save money on: Filling up on Tuesday afternoon or Wednesday morning will normally save you money: those are typically the lowest prices of the week. Also, filling up in the morning when the fuel pump is cooler will get you a few extra cents of fuel. So your best time to fill up is – on average – Wednesday morning. Don’t “top off” your tank: you risk losing fuel to the station’s vapor-recovery system, giving them back some of what you’re paying for. And speaking of that vapor-recovery system, some fuel refinery employees have reported that you’ll also get slightly more fuel in your tank by filling up with the gas handle on the SLOW setting so that you don’t create as high a fume content while filling the tank… but that may be “splitting molecules” with a benefit so small that it’s a waste of time.
- Use a good fuel additive. Injectors with excessive deposits have poor spray patterns that can cost you 2 to 10% in fuel economy. Those deposits are caused by poor quality fuel. Since ’95 the EPA has required all gasoline to have deposit-control additives. But as fuel quality control capabilities have improved over the years, average fuel quality has dropped steadily. Now about half of all fuel on the market is Lowest Additive Concentration (LAC) gasoline, which barely meets the regulation and contributes to excessive deposits. What can you do? First, if your vehicle is designed for premium gas, and you use premium, your injectors may be fine: many premium fuels include much higher additive levels that are effective at keeping injectors clean. However, what if you don’t use premium? Use “Top Tier” detergent gas if you can find it, because this new class of fuel meets the 2004 GM/Honda/Toyota/BMW deposit control standard. Shell states that all their gas grades meet the Top Tier standard.
If you don’t need to pay for premium and Top Tier isn’t available, you probably need an additive. BEWARE: there are a lot of mousey fuel additive products in ads and on store shelves that generate ridiculous sales profits but don’t do much for your vehicle. Find a good one that will clean your injectors, keep them clean, and (for diesels) lubricate your fuel pump.
The following fuel additives are some of the real products that do the job with quality, at low prices (follow the links for details). We know and use ALL of these products personally:
PI Performance Improver Gasoline Additive is designed to clean and maintain a gasoline vehicle’s entire fuel system and engine combustion components by dissolving and removing deposits and contaminants, and reducing friction in moving parts: injectors, pistons, piston rings, and heads all clean up to near-new condition. Naturally, that produces improvements in both higher fuel economy and lower emissions. This product has been formulated with latest technologies, to be the most effective and yet one of the most inexpensive products on the market. Add one $12 bottle to your tank every 4,000 miles, for optimal performance.
DIESELS: A similar fuel situation exists for diesel fuel, but true premium-grade diesel is non-existent or hard to find in most areas. Further, because ULSD can otherwise cut the life of fuel injectors and fuel pumps in half, Federal regulations require gas stations to add (for the first time) performance additives to the new Ultra Low Sulfur Diesel (ULSD), but most gas station and truck-stop employees seem to know nothing about this requirement. This means that the performance and life of your diesel engine and fuel injection system will benefit greatly from good additives:
Diesel Concentrate Performance Fuel Additive (one ounce of concentrate treats 5 gallons) is very effective in diesel engines to clean injectors, lubricate (critical protection against fuel pump and injector wear with the new ULSD fuel), reduce emissions and black smoke, and improve power & fuel economy. It extends engine oil life, prevents fuel/water mixing and protects metals against rusting, and is also safe for the latest exhaust emission systems such as diesel particulate filters (DPFs), meeting all Federal EPA requirements for Ultra Low Sulfur Diesel Fuel. Diesel fuel treated with this Diesel Concentrate easily meets the requirements of the National Council of Weights and Measures (NCWM) Premium Diesel Fuel Specification for resisting diesel fuel degradation. This product is also recommended as the ideal additive for Heating Oil Fuel.
Cetane Boost Diesel Fuel Additive (all diesel engines) also increases power and efficiency by increasing Cetane number (the equivalent of Octane in gasoline).
Diesel Cold Flow Improver is formulated with jet-fuel-type deicers to lower cold-flow-pour-point properties of ULSD diesel fuel as much as 34° F (18° C). Add this before each fill-up, to prevent wax & ice crystal formations from blocking your fuel filter in cold weather. This product works even better on biodiesel blends than on full petroleum.
An explanation will help:
The wax-crystal “cloud point” of some diesel fuels is as high as 40° F (4° C), and about 32° F is typical, meaning that when you pump it out of the underground tank into your vehicle in cold weather, it can start to plug up your fuel filter within an hour or less. (I found this out the hard way during my first diesel-truck winter: before adding this, the overnight temperature dropped to 26°F, and stuck me in my driveway for 2 hrs while I warmed up the engine with my block heater, and used a heat-gun on my fuel filter. Not anymore!)
- Shift your work-hours to avoid gridlock. Stop-and-go traffic kills fuel economy. Try to arrange traveling to/from work when traffic flow is running smoothly at the speed limit.
- Lose some weight! Reduce your vehicle’s weight: clean out the trunk (and maybe the back seat). Summer snow-chains, or tools from that weekend project months ago will cost you fuel! Every 200 pounds in your trunk costs you roughly 1 mpg.
- Don’t drive! Carpool, occasionally ride a bicycle or walk, telecommute for part of your work-week, or take public transportation.
- Park in the Shade: Some say the hotter the fuel tank gets, the more gas you lose to evaporation? Technically that’s true, but most of your savings will come from the air conditioner not having to work so much to cool off the “solar oven” of your car’s interior. When there’s no shade? Crack your your windows a bit, use a sunshade in the front windshield, and roll your windows down for one to three minutes to get the heat out. In general when you sweat less after getting in the car, you save money from your A/C not having to work as hard.
- Smart vacation thinking: If your vehicle is a gas guzzler, consider renting an economical vehicle to drive on vacation. With a discounted week-long rate at better fuel economy, the rental might pay for itself. If you lease your vehicle, using a rental vehicle will also lower your total lease miles.
- Keep a log of your mileage and fuel. I’ve done this for years, first in vehicle expense record books, and later with handheld Palm/Android/iPhone programs. One advantage is that you can monitor your fuel economy and driving habits. Not only can you learn the cost benefits of changing your driving style, but you can spot the poor fuel economy that is often a first-alert to maintenance issues. In addition, as you make changes to improve fuel economy, you can measure the exact results (averaged over a few fill-ups for better accuracy).
- Use your Fuel Economy display. One of the advantages to some of the most successful hybrids – like the Prius – is that they prominently display the instantaneous fuel economy. Many drivers have noted that this results in developing more frugal driving habits. If your vehicle doesn’t have this feature, you can add one, like ScanGauge.
Second: Vehicle MAINTENANCE & UPGRADES.
These areas often get skipped in fuel economy recommendations, but the impact can be huge. Now you can learn about these missing areas.
These fall into two general categories to improve fuel economy:
– decrease friction and other “parasitic” energy losses in the vehicle’s drivetrain (engine, transmission, differential, wheel bearings);
– make it easier for air to flow through the engine, from the air intake to the exhaust tailpipe.
These are the same areas that performance-enthusiasts improve to get more horsepower. I recently spoke with a Lexus mechanic who owns a Dodge 2500 pickup with the Cummins turbo-diesel engine. He was quite surprised that with his many thousands of dollars of horsepower upgrades, even running large tires and higher ground-clearance, he was getting about 23 mpg on a 2002 truck. “Every time I increased the power, the fuel economy improved.” No surprise to me: except for the tires, he was also increasing his engine’s efficiency with nearly every power upgrade.
1. Keep your engine tuned up. If you have a dashboard service-engine light on, you’re typically wasting fuel: for example, bad Oxygen Sensors are a classic problem that can cost you 5-15% in fuel economy. Overall, poor engine tuning and lack of maintenance will often decrease fuel economy by 5-20%, and it can be even worse in some cases.
2. Inflate your tires to their optimum design: HIGHER pressures than “normal”. Besides improving fuel economy, this will improve handling, increase safety, and increase tire life. Under-inflated tires can lower gas mileage by 0.4 percent for every 1 psi drop in pressure of all four tires.
Over 90% of car tires on the road are under-inflated, and this costs money in both fuel and in shortened tire life. “Experts” generally define the “proper” pressure as the vehicle manufacturer’s recommendation, and that’s what most service shops try to follow. Who can blame them when even the government says to follow inflation pressures on the vehicle’s OEM (Original Equipment Manufacturer) door sticker? Unfortunately, that’s seldom correct. OEM wheel/tire combinations for most cars and light trucks are designed by the tire manufacturer for inflation to between 35 and 42 psi [pounds per square inch]: far more than the recommended 28 to 33 psi that you’ll find in many owner’s manuals or on door-jamb labels. If your tires normally wear the tread off the shoulder before the center of the tire, you can be certain that your tires are under-inflated.
Vehicle manufacturers like to get the cushy ride quality by using under-inflated tires, rather than by using more expensive shocks, springs and suspension designs. What YOU need is even-pressured road-contact across the tread, because that gives you maximum tire life, better fuel economy, best performance in bad weather, and best overall handling and cornering characteristics. If you look closely on many tires, you’ll see a reference to 35 psi and a maximum pressure of 44 psi. So as long as you don’t put more than 44 psi in your tires, you’re fine.
So how much air pressure should you use? How do you figure it out? First, buy a digital pressure gauge – there are a lot of them for $8-20, typically accurate to a half psi or less. Or, you can use a mechanical-type gauge if it has a LARGE round dial. These bourdon-tube gauges are capable of good accuracy, but check the packaging to see how accurately it’s calibrated. Whatever you do, DON’T use a straight “stick” air pressure gauge. Stick gauges are typically inconsistent and inaccurate, reading 2 to 10 psi higher than actual pressure: your tires will always be under-inflated by at least that amount! (Yes, the newer vehicles have tire pressures on the dash display, if you want to keep sticking your head inside to read it.)
Next, inflate your front tires to about 40 psi and your rear tires to about 38 psi. (Most vehicles are heavier in the front than in the rear. If yours isn’t, maybe from stuff you haul in the truck-bed or trunk, then use the same pressure in all four tires.) Then watch how your tires wear. The ultimate is to buy a simple tire tread depth-gauge (max $6), and use it to check tread depth in the center, and near each “shoulder” of the tire (near the inside and outside edges) about every three months. If your tires wear more quickly on the edges, increase your air pressure by 1 or 2 psi. If they wear more quickly in the center, then decrease the air pressure by 1 or 2 psi. Most tires like to be in the 38-40 psi range, but if you put a wider tire on a stock-width rim, you’ll normally have to drop the air pressure to compensate and get an even pressure “pad” across the tread.
Results? By our conservative estimates, most passenger vehicles are riding on tires that are 8 psi low. (That 20% difference can also decrease tire life by an estimated 30% per the Technical Maintenance Council.) So overall, bumping your tire pressure up to the optimum will likely give you a 3% increase in fuel economy, depending on your vehicle, tires, and current air pressure. Plus you’ll also get ~30% longer tire life. Be sure to check/adjust your tire pressure monthly, increase tire pressure temporarily when you’re carrying loads, and rotate your tires twice a year or every 10,000 miles.
For more complete details, visit this excellent article on proper tire care.
3. Switch to best-quality synthetic oils and filters throughout your drivetrain: engine oil, transmission fluid, differential gear oil and wheel bearing grease. This advice – to use the best synthetic lubricants – is drastically neglected and one of the three greatest secrets in automotive maintenance, yet it’s an EASY area to save a lot of money because it’s just replacing petroleum with high-performance synthetics. The number of vehicle owners turning to synthetic engine oil has increased dramatically, which is very good news for consumers because synthetics are better than petroleum products in every way, BY DESIGN. However, it’s not a simple area to understand. So here’s a brief primer on synthetic lubricants with THREE KEY THINGS that owners don’t realize :
- First, that the benefits of synthetics extend to every lubrication area in the vehicle, including ball-joint grease. For example, most differentials and transmissions fail because their fluid has failed long ago, either because the fluid hasn’t been changed frequently enough, or because the fluid overheated in towing. Synthetic transmission fluid helps hugely to prevent problems, and naturally saves fuel at the same time. My ’94 Taurus SHO got 10% better car fuel economy with engine oil and transmission fluid change, my ’02 Sierra 2500HD Duramax got 8% better truck fuel economy with just synthetic engine and differential fluids, and a friend’s ’99 Olds Silhouette van picked up 20% just by changing to synthetic engine oil – saving over $600/yr in fuel. See other customer results. In other words, for most vehicles, real synthetic lubricants are one of the biggest and easiest improvements that you can make to improve fuel economy – yet they are rarely mentioned!!! We’ve found that most people will get 2 to 12% improvements in fuel economy, IF they use AMSOIL lubricants, but less to no improvement with other brands. (No infomercial here – just facts with integrity.) Fleet testing results with AMSOIL oils and fluids in commercial vehicles shows an average 6.54 – 8.2% improvement in fuel economy. And 8% fuel savings is also the most frequent report from customers who change all their drivetrain lubricants.
- Second, not all “synthetics” are REAL synthetics. Today, in fact, most are fake synthetics because the lubrication industry has agreed that it’s OK to deceive you. (Here’s how to tell a true synthetic from a petroleum “synthetic”.)Why do you need real high-performance synthetics? Because in every way they are better than petroleum products – by design – and because they are uniquely able to save you the maximum amount of money with 25,000 mile drain intervals, while other “synthetics” are designed to maximize petroleum-oil-company profits by pulling money out of YOUR pocket.
Third, not all real synthetics are the same. As a Mechanical Engineer who has worked for years in automotive, and done extensive research (about me), AMSOIL is my extremely strong recommendation. Why AMSOIL? AMSOIL was the First in Synthetics in every lubrication area, they are normally the cheapest to use, they are designed for maximum performance and benefit to you (most lubricants are NOT), they are the most widely used in professional racing & performance companies, and they continue to lead the world in synthetic lubrication performance – usually by a WIDE margin. (Notice the 2007 chart above which compared the wear rate of the only 35,000 mile oil in the world against the competition – click on it for latest testing.) Hundreds of 4-ball Wear Test results in independent laboratories have proven for decades that AMSOIL lubricants are designed to consistently reduce wear (friction) to a far greater extent than even most synthetic lubricants. This wear-reduction is friction reduction that translates directly to better fuel economy, and longer-lasting vehicles. But it’s only one portion of the fuel economy improvements – here’s a more involved explanation.
- REAL Results! I’ve often heard people say they wouldn’t consider a different oil because their big-name (inferior) petroleum oil let them put 200,000 to 300,000 miles on an old vehicle with 3,000 mile oil changes. But, most oils can do that in modern engines. That’s whimpy “kid stuff” compared to using AMSOIL: the cost of that petroleum oil maintenance is much higher than the 25,000 mile oil changes we recommend, and in comparison it’s not unusual for AMSOIL-equipped vehicles to exceed 500,000 miles on the original engine and transmission (no internal engine or tranny work, just service-interval maintenance on plugs, belts, hoses, etc). More and more fleet managers are discovering that AMSOIL saves fleets money. The fact is that AMSOIL’s 25,000 mile/1-year oils (proven and guaranteed) and 100,000 mile transmission and differential fluids mean that it’s less expensive to use AMSOIL products than to use anything else.
- Real life! My ’94 Taurus SHO got 10% better fuel economy with engine oil and transmission fluid change, my ’02 Sierra 2500HD Duramax truck got 8% better fuel economy with just synthetic engine and differential fluids, an engineer friend (a DFSS certified Six Sigma Greenbelt) tracked an 8% improvement in his Dodge Magnum using Minitab, an acquaintance picked up over 20% on a 37 foot gas-engine motor-home, and my friend Phillip’s 1999 Olds Silhouette van picked up 20% just by changing to synthetic engine oil — saving him over $600/yr in fuel. (Read about thrilled customers.)
- Want proof? You want data from respected independent testing laboratories? Ahh –- so you know marketing claims are worthless! How about the pictures and report from a certified Lubrizol engine rater, on the teardown of the original engine from the million mile van? We also have overall comparative testing data for many specific oil blends, including Mobil 1: ASTM testing by independent laboratories. While all the oil companies run these tests because they’re required by the API and SAE, generally only AMSOIL publishes significant data, while the others rely on vague performance claims and clever marketing slogans. Beware: test results against generic “competitor A, B, C” are legally meaningless and tell you nothing. But published/advertised test data against named products is legally binding, with huge lawsuit potential from competitors.
- Yet AMSOIL has been publishing the data for three decades, naming the actual big-name products tested, and not one competitor has ever challenged the data accuracy! See overall comparative testing results against many specific oils, including Mobil 1. Remember, these impressive results aren’t just fancy advertising charts: they’re test data from standardized (tightly defined) tests by independent laboratories. Few companies will show legally-binding data based on standardized test parameters like this, because independent testing on their products will not produce favorable data to support their product claims. In comparison, hundreds of ASTM 4-ball Wear Test results in independent laboratories over years have shown that AMSOIL lubricants are consistently designed to reduce frictional wear and internal fluid-friction losses to a greater extent than even most synthetic lubricants. Friction reduction translates directly to better fuel economy and much longer-lasting vehicles. So how do you switch to AMSOIL lubricants and ultra-long-life filters? It’s easy. You can find what your vehicles need here, order products online and have them in a few days then take them to almost any mechanic shop, or chains like Pep-Boys, Firestone, or Wal-Mart auto center for installation. See converting to AMSOIL for more details, and e-mail us at if we can help in any way.
4. Improve airflow AROUND your vehicle:
– Keep your windows rolled up at speeds over 40 mph: you’ll feel a lot of air turbulence around the window, and the air-conditioning is probably cheaper than the fuel-economy penalty in additional wind-drag.
– Turn off the air and roll down the windows at speeds under 40 mph in the summer heat: the additional wind-drag is cheaper than the air-conditioning.
– Consider adding a truck bed cover, either soft-type or hardshell: they can give you a 1 to 2 mpg boost. What about dropping your tailgate to travel, or buying an “air gate” net or louvered tailgate to replace the stock part? Those are not as reliable – results depend on the vehicle aerodynamics, bed length, and the size and shape of what you do (or don’t) have in the truck bed.
– Reduce air turbulence under your vehicle: “ground effects” styling packages, or “off-road” packages which include protective underbody “skid plate” features, can help enough to add 1-3% in fuel economy. The downside is that these can make the vehicle more difficult to work on.
– Adding an air deflector to the roof of your vehicle when towing will also help by 1 to 3 mpg, but keep in mind that it will also reduce your non-towing fuel economy by about the same amount if it’s still on the vehicle when you’re NOT towing. (These air deflectors improve fuel economy by “kicking” the air up over the trailer, reducing the trailer’s wind-drag.)
– Loaded roof racks or cargo pods can cut 5% or more off your fuel economy. Fill the trunk first. A cargo rack that slides into a trailer hitch can be a better option: it allows you to carry extra stuff, still get into your trunk, and use less fuel.
– Sunroof air-deflectors can be handy, but they do cost you a bit of money. Removing the air deflector might save 1/4 to 3/4% in fuel economy.
5. Improve airflow into the engine. This can happen in several stages of increasing complexity, but the first place is the air filter, where air enters your engine. If your filter is dirty, that reduces fuel economy – up to 10% in the worst cases. However, there’s a conflicting problem. Conventional filters should NOT be replaced before the OEM’s recommended interval or they will increase your engine wear rate: they rely on the “dust cake” buildup to achieve effective filtration, which can reduce fuel economy.
Easy: Here’s an easy “no-brainer” improvement: Replace your air filter with nanofiber filters born from military/aerospace technology. (Released in 2005 with worldwide patents, reasonably priced.) You get pressure drop nearly as low as an oiled gauze filter while filtering out 100% of wear particles down to 3 microns (for real). Clean with an annual tap/shake/vacuum. No warranty problems. Click here for more info.
AMSOIL is the ONLY company offering direct-replacement nanofiber filters for autos and light trucks. In addition, here are the Universal Ea nanofiber filter cones to replace the oiled-gauze cone filters in most of the aftermarket air intake systems such as K&N, S&B, Volant, TrueFlow, Injen, AFE & AIRAID. The Ea cone filters provide equal or higher flow, but with Absolute Efficiency (98.7%) at 2 microns instead of 70% efficiency at 15 microns! (Wear particles are 2 – 25 microns.)
Notice the inverted cone in the ends of these filters, which provides additional airflow over the common original solid-end-cap filter designs.
Intermediate: The next thing to look at is the air-filter box design. Many OEM’s have a restrictive flow-path going into the air-box (to reduce engine air-intake noise by some small amount, or to reduce the likelihood of sucking water if you drive through a foot or two of water), with lots of internal stiffener ribs. Sure, the improved strength from stiffening ribs may enable you to stand or kneel on the airbox, but they often cause pressure-drop and turbulence. Also, the tube that runs from the airbox to the turbo or induction manifold tends to be smaller diameter and/or have sharper bends that cause a pressure drop.
There are two improvement routes: an aftermarket air-induction system, or a DIY approach.
Some DIY tips on further improving airflow:
The best route is to look at replacing the entire air-intake box, filter, and MAF tube (going from the air box to the engine) with an aftermarket “air intake” kit. Caution: single-layer oiled gauze filters won’t keep out many wear particles, and so produce higher engine wear-rates than OEM filters, plus their oil can cause reduced fuel economy and trouble with warranty coverage at many dealers by contaminating the MAF sensor wire.
Multi-layered oiled gauze filters are an improvement, but you still have the oil, and the wash & dry and re-oiling steps that must be done carefully. So choose wisely. We recommend going for the nanofiber solution if AMSOIL has one available for your vehicle, because nanofiber air filters are the BEST compromise between no filter at all and a restrictive stock filter, and they completely eliminate the use of oil. Most of the panel-style direct-replacement Ea nanofiber air filters have OEM certified fitment.
Most aftermarket air intake systems include a round conical filter, meaning they are an excellent choice if Amsoil has a nanofiber replacement filter to fit these systems – and they generally do. Check available cone-filter dimensions here.
At the bare minimum, your choice of intake should include a two-stage dual-density oiled-foam filter, which removes far more dust than most oiled-gauze filters. If you can’t get at least that in an aftermarket air induction system, then we recommend skipping it: upgrade to a nanofiber air filter, and consider modifying the stock airbox as we outline next.
(CAUTION. The following ideas may require careful thought and planning, and results will depend on the actual vehicle & air intake design, the quality of the plan, and the skill in executing the plan. In some vehicles, the most restrictive part is the air intake box and filter, while in other vehicles the air tube running from the filter to the engine is the most restrictive part. If you don’t upgrade the most restrictive portion, you will see little (if any) fuel economy increase. Furthermore, poor-quality modifications can cause problems not covered under vehicle warranty. Note that in cases of stop & go traffic on blacktop in hot weather with no wind, some engines may tend to overheat more easily with some of these changes, if the intake air temperature is hotter than before the modifications. So these areas are best left for engineers or thoughtful mechanics, and we’re NOT responsible for your results):
The air passage into the air-filter box is often much smaller in cross-sectional area than the air filter surface, creating extra pressure-drop. Many cars have a skinny “cold air intake” muffler, tube or baffle, often hidden in a wheel-well, which are also designed to keep the engine slightly quieter. These can be removed or modified for better airflow into the airbox. Some vehicles have replacement aftermarket “cold air intake” tubes that are available to maximize airflow while retaining the cold air intake function (cold air gives better fuel economy and helps prevent overheating when idling in hot weather). These replacement tubes are generally a good idea, but will generally produce only a small fuel economy improvement by themselves – zero to 3%.
Want to take it a step further? A Dremel moto tool with a straight drill-like routing bit (kits for $60 or less at Wal-Mart) will allow you to easily enlarge or cut open several windows in the airbox to increase airflow – it’s best to open up the front and the side away from the engine, as those directions will normally pull in the coolest air.
Cautions: NEVER add holes on the engine side of the filter, or the air will bypass the filter!! And again, in some cases this option can increase the likelihood of engine overheating when idling in hot temperatures, so consider carefully.
A hot-air gun is a quick, handy way to soften the internal baffles so that you can fold them down, maintaining more strength than simply removing them (it’s OK to do that on the engine side of the airbox, too). It can also help you smooth a radius into the airbox outlet without removing too much material: the larger the radius, the better the flow. (Caution: be very careful and thoughtful when making any changes to the engine side of the air filter. If any cracks or holes should develop down the road, your engine will be sucking in unfiltered air, causing a high wear-rate.)
Those easy, intermediate-level and advanced airflow improvements can realistically net you up to a maximum 8% improvement in fuel economy under towing conditions, but 2-4% improvements are typical. Beyond that, you can start looking at adding or upgrading a turbo or supercharger, or increasing the size of the air-to-air intercooler and piping…
6. Improve airflow out of the engine: Install an aftermarket exhaust system. These have larger diameter pipes and larger, less restrictive mufflers. My point isn’t to get louder, but to reduce “backpressure” losses which cut down on horsepower, torque and fuel-economy. Since increased noise is typical, and some systems are intentionally designed to be loud, you may want to shop for the exhaust sounds you do or don’t want. Borla is my personal high-quality favorite, because they tastefully design for great improvement without being overly loud.
Keep in mind that on turbo-charged engines, anything you do to improve flow (reduce backpressure) through the exhaust system will pay rewards in increased turbo pressure, faster spool-up, and of course, better fuel economy. So if a larger down-pipe out of the turbo is an available option, take it: that’s a useful upgrade that is sometimes overlooked.
7. Watch your transmission modes. Use overdrive when possible. Don’t use 4-wheel drive when you don’t need it. And when buying a new vehicle, consider your driving conditions and habits: if 4WD is important to you, you might want to consider AWD (All Wheel Drive) options for improved safety and automatic fuel-economy management of the drive system.
8. Upgrade to a more fuel-efficient vehicle. But be cautious. Everyone wants to make money from your vehicle change, so be sure to look out for your best interests. There are several ways to do this. First, beware of sticker price. Second, compare the fuel economy of different engine and transmission combinations. In some cases a larger engine actually gets better fuel economy. But spending a lot more money to get more fuel economy may not begin to pay you back before you sell the vehicle.
- Hint: hybrids and electrics are getting “hot” in the market, but they are often not worth the money. One reason is initial cost penalty, another is unrealistic fuel-economy claims, and another is high replacement costs for the big battery packs that these vehicles use to store and transfer energy. If that 56 mpg turns out to really be 41 mpg as a long-term test did in the ’05 Toyota Prius vehicle (Car and Driver magazine), and you spent $6k more than an equivalent non-hybrid, and you’re faced with a $2,300 battery replacement bill after 3 years and you only keep it for 4 or 5 years… well, the 36 mpg standard vehicle was a better deal.
- For many people, the smartest purchase is probably a modern turbo-diesel vehicle. Here are a few of the diesel advantages: the initial cost penalty of the diesel is similar to a hybrid, but you have no battery replacement costs; the REAL fuel economy is about as good as the average hybrid and it improves over the first 125,000 miles; it produces less overall environmental impact than many hybrids; mileage life is 300,000 to 500,000 (or double that if using AMSOIL lubrication and filtration); maintenance costs are lower (no spark plugs, no tune-ups, not restricted to dealer mechanics); diesel fuel is more flexible and secure in supply than gasoline because of the heavy commercial use and the fast growth in bio-diesel fuel (which has no environmental downside); and it retains higher resale value. See our diesel page. Diesel fuel prices remain artificially higher than gasoline, in what may be a coordinated effort to boost “big-oil” profit margins to their astronomical highs, and delay diesel growth in the US until the Big-Three OEMs and the oil companies are ready to handle the shift from gas to diesel that overwhelmed the European market. If this scenario is accurate, then diesel fuel prices may eventually be coming back down into a legitimate price range.
Back to comparing the ’06 Toyota Prius and ’06 Volkswagen Jetta TDI, their base price is about $300 different and their weight is within 300 lb, interior and trunk room are nearly matched, and 0-60 mph acceleration is within one second of each other. But the Jetta turbodiesel got 47 mpg in real driving, vs the Prius with 41 mpg, and the diesel engine will almost certainly provide greater reliability, durability, mileage life, and resale value. And as many long-term diesel owners know, the mpg of the diesel is going to eventually IMPROVE another few mpg once the break-in phenomena is complete. Volkswagen turbodiesels typically increase to 50-60 mpg somewhere in the 75,000 to 125,000 mile range – which is right in the neighborhood of the claimed mpg of the hybrids – which seldom seem to live up to their EPA press releases.
- But in all fairness to the hybrids, there are a few more considerations. First, hybrid technologies are the target of heavy investments: they are improving. (One of the more promising directions is hybrids using small turbo-diesel engines.) Second, there are great differences in performance and maintenance costs from one hybrid to another. For example, hybrids often show a large drop-off in winter fuel economy under certain conditions, partly for some of the same reasons that standard gas or diesel-engine vehicles drop off in fuel economy, but the battery power storage is an additional factor: battery efficiency drops WAY off in cold weather. Finally, driving habits appear to play at least as large a factor in hybrid fuel economy as in conventional vehicles. For example, a 10 mile Phoenix city commute vs. 2 mile Boston city commute, vs. a 30 mile Atlanta highway commute, vs. a 20 mile rural commute on state highways, will all show very different fuel economy pictures. Bottom line is this: if you want an accurate estimate of what YOU would get with a specific hybrid vehicle, you need to find an owner of that exact vehicle who drives under circumstances similar to yours.
Rudolf Diesel introduced his engine at the 1900 World’s Fair in Paris, running on peanut oil. For several years diesel engines ran on vegetable oils alone, getting an average of 30 percent more miles per gallon than traditional combustion engines. Soon they became the standard powerplant for trucks, buses, freight-haulers and boats. Then the oil-drilling companies developed a plan to take over the diesel fuel market.
The newest Ford, Dodge, and GMC/Chevrolet turbo-diesel pickups are all excellent choices that out-tow the gas engines, get 20-40% better fuel economy than the gas engines (15/22 mpg is a realistic city/highway achievement for some of the newest 3/4 ton diesels, which also get 13-17 mpg when towing), and meet very stringent emissions regulations. That’s why 60% of those “heavy-duty” pickup sales are now diesel. One of the most practical options in a light pickup is the Dodge RAM 1500 with the 6-cylinder diesel: it tows as effectively as the Hemi, but gets a remarkable 29 mpg! (If you’re a pickup truck owner, consider installing an AMSOIL Remote Bypass Filter system with synthetic oil to pick up 5-10% more fuel economy, and then stop changing engine oil. Just change filters every 25,000 miles/1-year when you send an oil sample to a lab for analysis!)
In 2005 the diesel car choices were the Volkswagen Jetta, Jetta Wagon, Passat, Golf, and Beetle, the Jeep Liberty CRD, and the 224 hp Mercedes E320 CDI sedan which was driven 100,000 miles in May 2005 by a round-the-clock team with no breakdowns and an average speed over 139 mph. Only a few cars then, but the selection began broadening in the 2008 – 2010 model years, as manufacturers can now bring the best diesel engine designs from the European market into the U.S. Chrysler offers SUV’s, Jeeps, and the RAM 1500 with a 6-cylinder diesel engine.
Diesel power and performance? The latest diesels have a real edge over gasoline engines, and some of the hottest sports cars in Europe are now turbo-diesel tire-burners, where 2/3rds of the vehicles on the road are diesel! Diesels are winning land speed records and drag races. In addition, diesels won or placed so highly in so many prominent European road-races in 2006 and 2007, that race officials are devising new diesel-only restrictions to “level out” the playing field to give gasoline race engines a chance. Drivers are learning that acceleration is really based on torque, not horsepower, and pound for pound it’s getting hard to out-torque a modern turbo-diesel.
9. Be cautious in your search for improved fuel economy: don’t waste money on fake fuel-economy “improvements”. Many products are either total fakes or hugely exaggerated. Most companies tiptoe around the truth, but we don’t. So here it is.
– If it’s an “oil additive” or engine “metal treatment” it’s generally a worthless product embroiled in lawsuits in a number of states, and if an oil additive claims a fuel economy improvement over 1%, you can bet that it’s either lying or it’s damaging to your engine. Lubrication engineers will tell you that oil blend is a highly engineered chemical package, and that if you want better performance the only way to get it is to buy a better oil in the first place, based on the test data criteria that you’re most concerned about – that’s also the cheapest method. Visit our “deep-dive” on oil additives for extensive details.
– Fuel treatments/additives and catalysts? There are some gains available here, especially if your vehicle has had a long diet of cheap LAC (Lowest Additive Concentration) fuel. (See #11 above for more info.) The biggest fuel economy factor is the injector spray pattern: a smooth one from clean injectors will be good fuel economy, while an uneven pattern from dirty injectors will produce poor fuel economy.
A BIG key question to consider is cost vs value. The answer is YES to some good fuel additives, NO to the many poor ones, and “WHY BOTHER?” to a lot of them. Fraud and deception are rampant.
- For example, in 2007 we were approached about offering a fuel additive that was gaining many excited customers. Ultimate ME2 was reportedly designed by an Asian chemical engineer and is produced by an Asian company to supposedly change the fuel’s molecular hydrocarbon chain structure for more efficient combustion… perhaps possible, but a claim that’s conveniently difficult to check. We suspected that it actually worked by just cleaning the injectors and engine, in which case it would not give any fuel economy benefit in vehicles with very clean fuel systems and combustion chambers. So, to test our theory, we used the Ultimate ME2 additive for about two months in two vehicles (one Ford car, one GM diesel pickup truck) that had already been running efficiently using the inexpensive high-quality fuel additives we listed above, and saw no measurable improvements even after following the suggested “disconnect the battery” procedure to let the vehicle computer reset. Yet the wholesale price on a bottle of Ultimate ME2 was a stunning $39 USD! We’ll give them the benefit of the doubt that the product improves fuel economy in vehicles with dirty injectors and valves, but our tests appeared to confirm our original suspicions. Sure, fuel prices were high enough back then that a 10-15% improvement would more than pay for that $39 bottle. But we would rather get better fuel economy using a high-performance $12 product once every 4,000 miles, than to spend $39 to treat several tankfuls and add it at every fillup. Wouldn’t you?
So beware what you buy: research it well.
– Fundamentally, if a mechanical or electronic aftermarket product isn’t improving airflow through the engine/exhaust, it’s probably NOT going to boost fuel economy. Some examples of “improvements” that WON’T save you fuel: airflow swirling devices (the air will naturally swirl anyway, and most of these devices actually create a flow restriction – additional pressure loss in the air intake, which reduces fuel economy slightly); computer “chips” or “tuners” – while a few can give you a slight fuel-economy boost (perhaps 1/4 mpg in a stock vehicle, more if modified or towing), they are generally designed to add more power by using more fuel. They certainly add horsepower and torque, but they will do little or nothing to change engine breathing characteristics by themselves. Some will swear that such systems have improved their fuel economy, but on close questioning, you may discover that they made another change or two at the same time (like a tune-up, air-intake or exhaust upgrade) – the things that ACTUALLY produced the improvement.
An exception is that some of the engine tuner devices for turbodiesel trucks may provide a few percent increase in fuel economy when towing, depending on conditions, trailer, the year & model truck, and other performance modifications that have already been made. In these cases, improved tuning is possible because it can take better advantage of the other performance upgrades that have been made – such as a cold-air intake, turbocharger upgrade, and larger diameter exhaust.
10. Cool off your air intake. Lowering the temperature of the air your engine inhales will deliver actual increases in horsepower and fuel economy, and methods below can total roughly 1-3% improvements. Cool air is more dense, easier to compress, and gets more oxygen into the cylinders, thereby creating more power with fewer combustion cycles. Under high engine loads or high outside temperatures this issue shows up the largest.
There are four ways to cool off the temperature of your intake air, and these approaches can be combined to increase the benefits:
- Use an aftermarket “cold air intake” design which pulls the air from a cool region outside the engine compartment. Many newer vehicles have this built into the OEM design, but most older vehicles do not.
- Route any turbo-compressed intake air through an intercooler. This intercooler looks like an extra radiator, and it goes in front of all your other radiators and coolers. Its purpose is to remove heat from the hot turbo-compressed air. Again, most newer turbocharged gas or diesel vehicles DO use an intercooler. BUT, if you replace the existing intercooler with a larger one that delivers more cooling, there will be a direct improvement in horsepower and fuel-economy.
- Insulate or block engine heat from warming the air. If there is less heat available to warm intake air in the engine compartment, then the intake air will remain cooler. This can take several forms, so follow along.
You can insulate the exhaust manifold headers, which is a huge source of engine compartment heat – by insulating them, more of the heat flows out of the exhaust tailpipe and the engine compartment stays cooler. On an increasing number of modern engines produced since about 2005, this was being included in the OEM design. But on older engines it’s not addressed. For the aftermarket (not OEM) this insulating is most commonly accomplished either with ceramic coatings (remove the exhaust headers and have them sent off for coating), or with high-temperature wraps. The insulation moves more of the heat out of the exhaust so that less is radiated into the engine compartment.
Another insulation approach is to insulate the air intake system itself from the engine heat. On a few modern engines this is being included in the OEM design. But in older engines and still on most new cars, it’s not addressed. This can actually be done all along the air intake route, but one of the biggest improvements is in insulating the air intake area above the engine. This is high-impact because the air intake manifold sits on top of the engine: a lot of heat rises from and radiates from the engine directly into the air intake manifold.
- Reduce the temperature under your hood by installing vents or louvers in the hood (or sometimes the fenders, depending on the vehicle and your preferences). Louvers are particularly beneficial in the Southern-most states, and for towing/hauling engines, and have additional benefits in extending the life of various parts and accessories such as your hoses, battery and alternator in hot climates, and enabling your air conditioning to work better. With sunny skies and temperatures above 90°F in stop-and-go traffic, the hot pavement contributes to under-hood temperatures that will commonly peak between 180 and 250°F.
As with any vehicle modifications, there are proper-installation caveats to consider such as louver location and rain gutters. But it can be well worth the time, money and effort: Louver vents will lower those under-hood temperatures by roughly 20-70 degrees, which will automatically lower the temperature of your engine intake air.
This calculator will allow you to see the horsepower difference that is made by a change in the “virtual temperature” of the intake air.
Oil Additive Deceptions
Federal Trade Commission
Diesel Owners Forum
Commercial and Fleet Savings with Amsoil (pdf in new window)
Gasoline Engine Fleet Case Study (pdf)
Controlled Class 8 semi testing shows 6.5% fuel economy improvement (pdf)
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Ultimate Fuel Economy Guide
Revision (Version): 19
Last Revised: February, 2016
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