My Fuel Economy Page

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Free Fuel!

Remember the phrase "Your Mileage May Vary?" Well, it's more true than you think. Since most people get consistent mileage from one 300-mile tank to the next, they have no idea how wildly their mileage varies while they're driving, because it's all averaging out. The trick is to consistently identify and limit the situations that get the worst mileage and maximize the situations that get the best mileage.

With only a little practice, I was able to permanently improve my average by over 30% over the course of a few weeks. It was like getting a free tank of gas every month! In the first year of adopting these techniques, I saved 150 gallons of fuel and about $500.

You don't have to drive like a grandma (or a lunatic, or a jerk) to accomplish this. The media have devoted a lot of negative coverage lately to extreme fuel-economy techniques. Don't believe the hype. You can get fantastic mileage without doing anything dangerous or stupid. You just have to learn what helps your fuel economy and what hurts it.

Here's a short list of the basic techniques that anyone can do to save fuel. Click on any of the underlined words to link to the more detailed explanations below:

  • Air up your tires. Your car's door jamb only shows the minimum pressure. The maximum pressure, which is stamped on the sidewalls of your tires, will save you 5-10% on the highway and is perfectly safe.
  • Ease up! Accelerate at 1/4 to 1/3 throttle, keep the engine revs down, and keep the speed down.
  • Minimize braking by anticipating speed changes, timing lights to hit the green, leaving enough room in front of you, only using the throttle when it will get you somewhere and coasting as much possible. This one is difficult but important. Read below for more details.
  • Avoid idling. Kill your engine whenever you're parked, and at longer lights.

    • How To Do It

    The Basics | Next Steps | Equipment | Stuff I Don't Do

    In addition to equipment choices that can affect your mileage, there are techniques you can adopt that target and minimize specific situations in which fuel is typically wasted. Some are easier than others. Some cost money and others are free. You don't need to drive a hybrid, and you can do this without doing anything that is unsafe, bad for your car or illegal!

    Techniques - The Basics

    First, the tips with the biggest bang for the buck and/or effort. These require minimal sacrifice except possibly your ego, and everyone should practice them:
    Air up!
    		 The tire pressure indicated on your door jamb is simply the pressure recommended by the automaker for comfort. In fact, it is a minimum pressure and not a maximum. The maximum pressure (usually 44psi) is stamped on your tire sidewall. Inflating your tires to this pressure when cold is not overinflation, will not cause premature wear, and actually reduces your risk of blowouts. There is an enormous safety margin built into this pressure rating, and your tires are designed to be run at this pressure! Savings: Medium.
    Cost: Free to 75 cents.
    Difficulty: Easy.
    Ease up!
    		 Proportionally, speeding costs you more in fuel than it saves you in time. Above 60 mph, a 10 mph jump in speed increases wind resistance by over a third and costs you 20% more fuel.
    • Keep your speed down on the highway.
    • When accelerating, ease up on the gas and try to upshift by 2000 rpm. Avoid unnecessary downshifts.
    • Don't waste too much time in your first couple of gears. 1/4 to 1/3 throttle yields better fuel economy than feathering it.
    • Allow your speed to drop on uphills and rise again on downhills.
    		Savings: Huge.
    Cost: Free.
    Difficulty: Easy.
    Minimize braking.

    		 For urban driving this is the most important tip -- but takes the longest to learn and is the hardest to understand. It also requires the most concentration, so get out of the habit of using the cellphone or other distractions while driving or you will never get this one right.

    Braking wastes all the momentum that you've burned precious fuel to build up, and is why most cars get lower mileage in town than on the highway. If you're braking a lot, it means you've been on the gas too much!

    • Leave enough space in front of you that you don't have to speed up and slow down as much as the vehicle in front of you. This also helps smooth traffic flow.
    • Keep your speed down in city traffic.
    • Learn to anticipate stoplights (and their timing) and stop signs. Coast up to them as much as possible.
    • Don't race up to stop signs and red lights. Get off the gas long before you get on the brakes.
    • Roll through green lights instead of fully stopping for red ones whenever you can. That might mean a little braking early on, but can be worth it if it means not braking to a full stop later.
    • Accelerate only when it will get you somewhere, and coast at all other times.
    		Savings: Huge.
    Cost: Free.
    Difficulty: Moderate to advanced.
    Avoid idling.
    		 Idling wastes a surprising amount of fuel: anywhere from 1/2 ounce (on a small 4-cylinder) to 2 ounces (on a big V-8) per minute, and those figures can double with the A/C on. Never let your car idle while parked, and also kill the engine while stopped at longer lights. The idea that restarting an engine takes a lot of fuel is a myth left over from the days of carburetion. Restarting today's engines takes less fuel than idling for 10-15 seconds, and won't hurt your starter. When in doubt, kill it!

    		Savings: Small to medium.
    Cost: Free.
    Difficulty: Easy to advanced.

    Techniques - Next Steps

    The next set of tips offer require more advanced techniques, commitment or sacrifice, or offer more modest gains. Still very much worth considering for the serious hypermiler. Do what you're comfortable doing, and don't feel guilty about the rest.
    Pulse and Glide.
    		 Once you've mastered the above, this is the big one. Here's the deal: most engines operate most efficiently under a moderate load. But believe it or not, steady speeds present a very light load to almost all modern engines -- even on the highway. If traffic permits you to vary your speed by 5 or 10 mph, you can save large amounts of fuel by alternately "pulsing" at a moderate rate and then coasting. If you do it right, you may find yourself spending more time coasting than pulsing! It can take a while to find the sweet spot -- usually 20-40% of the engine's power -- but on a smaller car this alone save you 10 mpg. Savings: Medium to large.
    Cost: Free.
    Difficulty: Moderate to advanced.
    Park strategically.
    		 Minimize fuel wasted in parking lots:
    • If possible, park where you can drive straight in and out without backing up.
    • If you know you're going to have to back out of a space, back in instead! Better to back up with a warm engine, and later use the engine's fuel-rich restart cycle to help move the car forward instead of wasting it moving backward.
    • Whenever feasible, coast in to the highest spot on the parking lot, and coast back out to the exit when you leave.
    • Minimize wasteful low-speed trolling. Avoid busy pedestrian areas and park as close as possible to the entrance and exit.
    		Savings: Small to medium.
    Cost: Varies.
    Difficulty: Easy to advanced.
    Start warm.
    		 Engines are very inefficient when cold. If you have the option to park in a garage in winter, do it. If you live in a colder climate and have a block or coolant heater, use it. But make sure to put the thing on a timer so it doesn't jack up your electric bill by running all night. Savings: Small to medium.
    Cost: Varies.
    Difficulty: Easy to advanced.
    Limit A/C use.
    		 Look, sometimes you need it. But A/C increases your fuel consumption by 10% to 20% while driving, and can triple your consumption while idling. So get along without A/C whenever you can stand to. Use a sunshade or park facing north on sunny days. If your car's hot from parking in the sun but it's not that hot out, blast the A/C for a few minutes, then kill it.

    However, be aware that at highway speeds it is more fuel efficient to run the A/C than to drive with the windows open.

    		Savings: Small to medium.
    Cost: Free.
    Difficulty: Easy to moderate.
    Engine-off gliding.
    		 First of all, this is a way to incrementally improve your fuel economy, only after you've mastered all of the above. You can get great mileage without doing this. If you're not completely comfortable doing it, then skip it. It should only be done by a highly competent and attentive driver in a small to midsize car who is comfortable doing it, and only under the right circumstances.

    The first time you do this, make sure to do it in a big empty parking lot where you can get comfortable with how your car behaves without the engine running. If you don't get comfortable with that, then don't attempt it on the road!

    To do it, turn your key back to the ACCessory position for a second or two until your engine dies, and then immediately turn the key back to the RUN position. With the key in RUN mode the steering wheel won't lock, and your ABS and airbags will continue to function even without the engine running. Your wheels won't fall off, and your car won't explode.

  • You will lose the power assist on your steering. Your car will handle pretty much the same as a car without power steering at all, something that used to be normal on small cars until the mid 1990s.
  • You will lose your power brakes after 4-5 pumps of the pedal. One pump is enough to fully stop you from 60 mph. Once you've touched the brakes after killing the engine, however, it's time to restart.
    		• Savings: Small to medium.
    Cost: Free.
    Difficulty: Very advanced.

    Equipment Choices

    Monitor your fuel economy.
    		 To get the feedback you need to improve your mpg, you need a resettable trip mileage display. Most people get an immediate 10-20% jump in mileage simply because of the instantaneous feedback. Any car built since 1996 has a diagnostic port under the dash into which you can plug a device like the ScanGauge II. Get one. Savings: Medium.
    Cost: $160.
    Difficulty: Easy.
    Buy Low Rolling Resistance tires.
    		 This could cost you nothing if you do it when you're buying new tires anyway. Consumer Reports tests tires for rolling resistance. Many Michelin models roll well and are clearly identified as such on their website, and the better Toyo touring radials offered at Northwest Les Schwab stores are also quite efficient. Savings: Medium.
    Cost: from free to $500.
    Difficulty: Easy.
    Clear the roof.
    		 If, like many Northwesterners, you have a roof rack loaded up with attachments for cargo boxes and sports gear, you may not realize what it's costing you. Even a bare rack without accessories costs 1-2 mpg on a midsize car. Add a bike or cargo box, and the damage jumps up to 4-5 mpg. Trunk/hatch or hitch mounted racks can carry cargo, skis and bikes, and cost far less in terms of fuel economy. Savings: Medium.
    Cost: Varies.
    Difficulty: Varies.
    Buy a more fuel efficient car.
    		 Hybrids and diesels are great -- as are less expensive economy cars -- and can save you a lot of fuel. But changing cars can cost you many thousands of dollars or require a major lifestyle change. Since most of the above techniques are free or very inexpensive, learn to drive efficiently before spending thousands on a vehicle purchase! And then, if you later do trade in for better fuel economy, you'll get really good mileage!

    Some of my favorite fuel efficient vehicle choices are listed on my Cars web page.

    		 Savings: Potentially huge.
    Cost: Varies widely.
    Difficulty: Varies widely.
    Drive a stickshift.
    		 If you're already buying a car (see the previous tip), get a stickshift unless you're buying a hybrid or your physical condition prevents you from using a clutch. If you can master the above techniques you can certainly learn to drive a stick. Manual transmissions are more efficient than automatics, and allow much more effective use of the techniques I've described above. Unfortunately many manuals are geared lower than automatics to provide responsive top-gear acceleration, but thanks to the additional control you get with a manual you're still likely to get better mileage. Savings: Small to medium.
    Cost: Negative.
    Difficulty: Easy to moderate.

    Stuff I Don't Do

    NO truck drafting
    		 I do not draft trucks, and I do not recommend it. Never drive next to a truck or follow closer than 2 seconds. It's not worth the risk. Don't think a big SUV or pickup with "more metal around you" will make this safe, either. A loaded semi weighs 80,000 pounds and will squash your F-250 like a bug. Stay away.

    I repeat: NO DRAFTING!

    NO extreme cornering
    		 While it's true that slowing down unnecessarily for curves and corners can waste fuel, it's not worth it to go racing around corners at the expense of safety.
    • Don't push your car past the point where the tires start to squeal. If you hear squealing, back off.
    • Be careful with very high performance cars and tires. They tend to give you much less warning as they reach their limit, and their higher limits get you into trouble faster.
    • Be careful with low performance cars. Softly sprung SUVs and minivans can be harder to control near their limit and can more easily roll over.
    • Slow down for corners when it's wet or especially when it's snowy or icy.
    • Never take a corner or curve faster than you can see around it! If your stopping distance is further than you can see, you're going too fast.
    NO ignoring pedestrians
    		Our roads can be a pretty unfriendly place if you aren't in a car. Let's all do our part to make it easier. It just might get us out of our cars more. That's good for both our economy and our health. Even a hypermiler can afford the tiny extra amount of fuel.
    • There's absolutely no excuse for failing to stop for a pedestrian in a marked crosswalk. Even on a multi-lane road.
    • You should already be paying enough attention that you don't need to stop abruptly. The old "but I could get rear ended" excuse is bogus.
    • On a multi-lane road, stick your hand out the window to indicate why you're stopping and discourage others from going around. It really works!
    • All intersections have implied crosswalks unless marked otherwise. You must stop for a pedestrian waiting to cross. Most people don't, but that's no excuse.
    Aero modifications??
    		 Things like smoother hubcaps and smaller mirrors can easily save a couple percent, underbelly pans and wheel skirts may save yet more, and extreme measures like big air dams and boattails can yield huge fuel savings on the highway. But this is strictly DIY stuff that requires major effort and/or expense relative to the savings involved, and can have significant safety and legal consequences. If you're an accomplished and determined DIYer, by all means visit some online forums first (to find out what actually works), and then have at it. Otherwise, don't bother.

    My mpg

    My Current mpg

    Since early 2008 I've been driving a (gas-powered) VW Jetta Wagon originally rated at 24/31 mpg. I record my fuel usage at     cleanmpg.com. Here's how I'm doing so far.

    My Initial Results

    Following are my Subaru's overall average from May 2007 through January 2008, and a graph of fuel economy versus daily high temperature over time. Note how mpg improves in the warmer months and goes down in the cooler months.


    Prior to starting this exercise, I had consistently gotten mileage in the low 20s in the city and low to mid 20s on the highway on all 3 of my Subarus. In 2006 I made a conscious effort to drive less enthusiastically around town, but this only netted me a gain of 1-2 mpg. Even after the change I got about 21-22 in town in winter, 23-24 in town in summer, and 23-26 on the highway. The highway mpg was so poor due to high speeds (all too frequently in the mid 70s) and the presence of a roof rack frequently laden with a cargo box and/or bicycles.

    Then in the spring of 2007 I started reading up on "hypermiling" and various techniques used to improve fuel economy. Up to that point I had assumed the 1-2mpg improvement from easing up on the gas was about all I could get. I never imagined I could see the 30% improvement I have achieved since I got serious about it that May.

    • First 4 tanks were in the 28-29 mpg range. This was as I was first trying to learn how to drive for fuel economy.
    • After the first 4 tanks, my mileage abruptly jumped into the low 30s and stayed above 29 until October. This was due to my acquisition of a ScanGauge and the ability to actually see in real time how my driving affected my fuel economy.
    • In August, my mileage started sagging down into the 30-31 mpg range as my Subaru's aging battery started to give out and I could no longer kill the engine when I was not using it.
    • In September my mpg spiked when I took a long roadtrip at moderate (55-65 mph) speeds and achieved a 500 mile tank at 35 mpg.
    • October and November saw the expected seasonal downturn in fuel economy, with mileage settling down into the 27-28 mpg range. This period also included only city driving except for a a 600 mile roadtrip in late November that yielded 31 mpg.

    Links

    • cleanmpg.com, founded by Wayne Gerdes (the godfather of Hypermiling), is a wealth of information on driving for fuel economy. If you have additional questions about the techniques I've described, register for the forums on this website and ask away, and it's one of the nicest groups of people on any Internet forum.
    • cars.html on this website describes the fuel efficient vehicles that I recommend.
    • fueleconomy.gov is the source for specific fuel economy ratings of vehicles going back to 1985.
    • edmunds.com is the best place for general reseach on cars going back to 1990, and has a Green Car Guide full of excellent articles related fo fuel economy.
    • gassavers.org is another good source of fuel economy information.
    • Numerous sites for specific fuel efficient cars, such as priuschat.com, tdiclub.com, fitfreak.net, metrompg.com, yarisworld.com and insightcentral.net have active discussion boards related to fuel economy. Go in with a thick skin though, because many of these forums have a lot of inexperienced, aggressive drivers who may be hostile to your ideas.
    • The Tufts Climate Initiative issued ratings of carbon offset companies in 2007. Native Energy and Atmosfair are among the recommended choices.

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