How to Improve Your Gas Mileage (and How Not To)

With gas prices on the rise, I thought I’d highlight an article I found on Consumer Reports about ways to save on gas… and ways not to. Given the results of my latest experiment on improving gas mileage, I can vouch for pretty much all of these.

1. Drive at a moderate speed. Keeping a lid on your speed is the #1 thing you can do to improve mileage. In their test car (a Toyota Camry), CR estimated that mileage dropped from 40 mpg to 35 mpg when they increased cruising speed from 55 mph to 65 mph. Speeding up to 75 mph dropped mileage another 5 mpg. While the extent of the drop will vary across makes and models, keeping an eye on the speedometer — especially when driving on the highway — will save gas.

2. Drive smoothly. Avoid rapid acceleration and hard braking. Once up to speed, try to maintain a steady pace. Jackrabbit starts burn excess gas, and unnecessary braking just converts energy gained from burning gas into heat (and it wears out your brakes).

3. Reduce unnecessary drag. Even empty roof racks can reduce mileage. Try to keep your luggage inside your vehicle, and if you’re not using your roof rack, remove it.

4. Don’t use premium fuel if you don’t need to. If your car is designed to run on regular unleaded, putting in premium won’t help. Using premium won’t hurt, but you’ll be spending an extra $0.20 per gallon for no reason.

5. Minimize driving with a cold engine. Engines run most efficiently when warm. Try to group errands together. This not only minimizes back and forth trips, but also maximizes efficiency by not letting the engine cool off too much.a

6. Keep tires properly inflated. Underinflated tires can cause a number of problems, not the least of which is reduced gas mileage.

7. Buy tires with lower rolling resistance. Less friction = less wasted energy, which translates into more miles per gallon. Believe it or not, this can account for a 1-2 mpg difference.

8. Avoid idling for long periods. If you’re burning gas, but not going anywhere, you’re getting zero mpg.

What Doesn’t Make a Difference

And here are three gas myths that don’t help at all:

1. Morning fill-ups. I’ve heard on more than one occasion that you should buy gas in the morning because it’s cooler, and the gas will be denser. The argument goes that this will result in more gas for your money. Problem is, it’s not true. Gas is stored underground, and the temperature barely changes at all over the course of the day.

2. Air conditioning vs. opening windows. While air conditioning can reduce your mileage, so does opening the windows. But in their tests, CR concluded that both effect were negligible. Note, however, that this testing was done at highway cruising speeds. I suspect that air condition might have a larger effect in stop and go traffic.

3. A dirty air filter. A popular recommendation at oil change places is to replace your air filter since a dirty filter supposedly reduces mileage. That being said, CR’s results indicated that, unlike the case with older cars, the mileage of newer models is unaffected by a dirty filter. The reason for this is that modern engines can compensate for a dirty filter and keep the air/fuel ratio constant.

21 Responses to “How to Improve Your Gas Mileage (and How Not To)”

  1. Anonymous

    I have a Toyota Camry and when going up hills i will creep up a few mph and then hold the throttle and not let it shift out of overdrive unless i am impeding on traffic

  2. Anonymous

    Would like to know if, when driving 18 miles to my club, am I better off to take the tollroad ($1.50 each way) and drive 65 mph or the stop-and-go route, no toll? My PT Cruiser gets 16-18 mpg. Yuk. Also, is it more economical to have AC fan higher or temp cooler? Or is there no difference?

    Many thanks.

  3. Anonymous

    About accelerating — the old truckers saying is accelerate as if there were an egg between your foot and the gas pedal.

    Anticipating traffic light changes in light traffic can increase mileage. Brake before you have to and creep up to the light so you are still rolling instead of driving up and then braking to a stop helps a lot.

  4. Nickel

    drewzr: That’s what I’ve always thought, too. However, based on CR’s test data, at least for the car they tested and the conditions they tested it under, there’s no difference. Of course, the best of all possible worlds is windows up and AC off, which is what you’re essentially doing when you recirculate the cool air after shutting down the AC (I do this, too).

  5. Anonymous

    About myth #2, opening windows is better in city traffic, but on the highway it’s better to use the air conditioning. Or, you could do what I do and use the vent. If it’s too hot for that, I usually set the vent to ‘recirculate’ and turn the AC on until it’s cold enough, then turn it off. When it gets too warm again, i turn it back on.

  6. Anonymous

    I like the point about tires. I agree with Scott and wonder if there is some sort of system for rating tires. I actually am in the market for a new set of tires so if I find something I’ll be sure to post it. Thanks for the ideas.

  7. Anonymous

    Is there a rating system for finding tires with the best (least) rolling resistance? I have the Michelin Energy tires which are supposed to have been designed with this in mind, but I was wondering how one might compare brands? Great list!

  8. Anonymous

    The problem with point #2 is that there are a lot of people who interpret “avoid rapid acceleration” to mean that they should creep away slowly from a traffic light rather than getting up to speed. Among other things, this tends to cause the people behind them to brake, if they were accelerating at, you know, a normal pace.

    The trick is to find the happy medium: don’t burn rubber when the light turns green, but do move smoothly into higher gear at a good pace.

  9. Anonymous

    There is an import fact missing from myth #1 (morning fillups). While filling stations tanks are underground, the tanks where fuel trucks get the gas that they deliver to the filling station are above ground. I work in this industry and the fuel terminals, where gas stations buy the gas they sell, calculate the net quantity that they charge to the filling station by compensating for variations in temperature to one-tenth of a degree.

    So if gas has sat overnight in an underground tank, it cools to ground temperature and is then more dense giving the buyer more energy per gallon. If you buy later in the day, a truck may have recently delivered “warm” fuel to the station, with less energy per gallon.

  10. Anonymous

    Regarding the morning fill-ups, here in BC the pumps are calibrated- there is a little sticker that reads “volume corrected to 15 degrees”
    Do you not have that in the US?

  11. Anonymous

    Moose- Most modern cars have a computer that will adjust the fuel mix so there is no need to ‘warm up’ an engine anymore.

    FWIW, if you are going idle for more than a minute, you can turn your engine off.

    If you want to know more, try CarTalk at They frequently answer gas mileage questions and that’s where I learned those two things.

    Nickel- I agree that steady ground temperature means that morning fill ups are a myth, but when the ambient temperature fluctuates 40-50 degrees from day to night (like in the desert), it might actually be true if the ground temp is also moving say, 30 degrees. Has anyone actually studied this?

  12. Anonymous

    I recently stopped starting our car in the morning to let it “warm up” before taking off for the day. Well to be more accurate, I stopped letting it run for 5-10 minutes and instead cut the time down to about 2-3 minutes. With gas prices going crazy, I figured even if it saved me a little bit of gas it was worth it. Any opinions if idling really causes major gas loss?

  13. Anonymous

    I think Morningfillups should make a difference as even the ground/underground cools over night.

    In my experience, in city traffic..Air conditioning has an effect (by couple of miles/gallon) on mileage.

  14. Anonymous

    Couple points here.

    You don’t change air filters for mileage, you change them to keep grunge and dirt out of your engine. Change them when the manufacturer recommends.

    Also, driving is not a game. It’s not a competition to see who can beat whom with the penny savings. It’s a serious $#@! activity, and the hypermileridiots who turn off their cars to save a dime every 100 miles by threatening their own, and others safety deserve a special place in road rage hell.

    Lastly, and I know this is a nit, but premium fuel may actually HELP /mileage/, but not enough to outweigh the costs. (So I agree with the spirit of the tip, just not the letter.) Again, put in what your car manufacturer recommends. THEY actually do test that stuff out and not rely on anecdotes.

  15. Anonymous

    Oh man, thanks for clarifying myth #3 – the dirty air filter one. I’m always hearing that from the mechanic and tempted each time 😉

    I do change it, don’t get me wrong, but i didn’t think it was 100% necessary during EVERY oil change.

  16. Nickel

    Yeah, what I’ve read seems to agree with Aaron’s thoughts. Hypermilers tend to focus on acceleration when going downhill, and are content to lose speed uphill rather than racing the engine to maintain speed while working against gravity.

  17. Anonymous

    Good post nickel. I can vouch for 1 & 2 also. I went from averaging about 30MPG to 36MPG in my xB just by trying to be mindful of my speed and acceleration. Slowing down early for lights (coasting) helps too.

    KITTY- My reading on the hypermilage sites leads me to believe that steady pressure on the gas pedal is better than a steady speed. You may only go 50 on the uphills, but you’ll go 75 on the downhills. Seems like it may not work, but I think it does.

  18. Anonymous

    Any tips for driving on a mountain parkway that goes up and down a lot? It seem to me that in this conditions, maintaining a constant speed may not be a good idea as it would entail pressing hard on gas when you go up and breaking when you go down. Wouldn’t allowing the car to slow down when going up and allowing it to speed up naturally when going down would make more sense in these conditions?

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