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4 gas-saving myths

money.cnn.com — Using a special additive or cutting off your A/C won't really cut your gasoline consumption. But myths like these run rampant in the minds of American drivers

Who dugg this? Made popular May 10, 2007

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  • Buttercup, on 10/12/2007, -13/+301i find that my car's optimal speed limit is 0mph. i hardly ever run out of gas that way.
  • LogicBomB, on 10/12/2007, -8/+136I think I can safely speak for the rest of us when I say drive AT LEAST the speed limit. Don't be "that guy" driving 50 in a 65...
  • tom6a, on 10/12/2007, -2/+129I like the tips you can trust:

    * Make sure your tires are properly inflated.
    * Removing excess weight from your car
    * Use cruise control.
    * Drive the speed limit and avoid rapid starts and stops.

    Here's another good article on how to improve fuel efficiency:

    Improve MPG: The Factors Affecting Fuel Efficiency
    http://www.omninerd.com/2006/07/16/articles/57

    Looking at the other side of things, here is a well-researched article on why maybe we fret too much about gas prices. According to this article, "saving money on gas is important, but the hype around it may cause undo attention, especially considering the amount of money that could be saved on other things."

    Gas Prices in Perspective
    http://www.omninerd.com/2006/09/15/articles/59
  • strangewill, on 10/12/2007, -8/+101What do you mean AC doesn't consume more fuel? Not only was this on mythbusters, but it's common sense that the extra horsepower subtracted from the engine to power the A/C is going to need to be replaced with more gas.

    I drive a 100hp 1992 civic, so I can TELL when there is a difference in gas mileage and power loss due to A/C. And due to the fact I get 35/45mpg, yeah it cuts into my mileage a bit.

    Now, when you're pushing 300hp and have 24/27 mpg... yeah who the hell cares.


    Best way to save gas: Don't drive like a dick, seriously you'll save gas.

    Anyway, buried as inaccurate.
  • VnutZ, on 10/12/2007, -8/+80Ummm ... dude, cutting your A/C dramatically saves on gas. From the article Tom6a cited, driving at 65mph in 6th gear with A/C on uses as much gas as driving 65mph revving your engine in 4th gear. Another popular myth is that by driving faster you save gas because the engine is "off' longer. Doing some math on a 1000 mile road trip shows that for certain coefficients of drag, driving slower for five more hours uses ~25% less gas than arriving five hours earlier by speeding.

    You want to save gas ... slow down.
  • geoken, on 10/12/2007, -14/+82I don't think you can really make a blanket statement about driving the speed limit. Every car will have a different optimal cruising speed just as many roads have different speed limits. A better method would be to make yourself aware of your car's optimal cruising speed. I think this belief is aided by the myth that lower rpm = less fuel, which isn't neccessarily true in todays modern cars. If anyone has ever seen a graph of fuel consumption vs. rpm / rpm while the engine is under load (ie a dyno) you'll notice that the engine has an rpm vs fuel 'sweet spot'.

  • Odiwan, on 10/12/2007, -9/+72Simple physics: Air conditioning takes energy. The energy has to come from somewhere. Guess what? It comes from the gas.

    Odi
  • Elias1, on 10/12/2007, -13/+55Driving the speed limit really makes a difference.

    I've averaged 22mpg since I started keeping track 5 years ago. By just driving the speed limit to and from work (30 miles each way) and making no other changes, I've bumped my average to 26mpg. It saves me about $70 a month.
    Drive behind a big rig at below the speed limit and you'll save even more.
  • nexah3, on 10/12/2007, -4/+41I like to roll with my windows down blaring my Bill O'Reilly.
  • TransFrat, on 10/12/2007, -3/+39"You realize you are getting 0 mpg when you aren't moving, right? 0 tends to be a pretty crappy mileage, regardless of your vehicle."

    Erm. No. He's getting 0 miles for 0 gallons, not 0 miles per 1 gallon. 0 / 0, not 0/1.
  • mygrayarea, on 10/12/2007, -3/+38Personally I prefer the A/C on with the windows down.
  • ninjacob, on 10/12/2007, -0/+33The A/C changes load, not RPM. When the A/C clutch is engaged the load on the engine will change, which effects your fuel consumption.
  • Dayz, on 10/12/2007, -1/+33in the picture. the person is paying $4.25 a gallon. where the hell is that
  • RedHerringHack, on 10/12/2007, -3/+31Stop signs and Red Lights waste gas. Let get rid of em. j/k
  • rollem, on 10/12/2007, -2/+28How fast do you usually accelerate a person?
  • tdogg241, on 10/12/2007, -4/+26I think there was a Mythbusters about A/C vs. driving with the windows rolled down. IIRC, the difference when driving around town was negligible, but when driving on the freeway they found it was slightly better to use A/C with the windows rolled up (even then, it was only 1-2% increase in fuel economy).
  • rollem, on 10/12/2007, -1/+22None of the additives work, if they did they would be added to the gas. Furthermore, none of the additives which have been independently tested have shown to improve gas mileage. And don't tell me "I've used them, I know they work..." Any test you may have done had exactly one repetition, unless you have multiple, identical cars, and had so many confounding variables that you could never say that the additive is what affected your mileage. For example, you probably drove slightly differently with the additive in, not wanting to prove your stupidity by buying the additive and having worse mileage. Not to mention weather, driving conditions, etc.
  • archlich, on 10/12/2007, -4/+22They're not talking about if using ac uses gas, of course it does.

    They're saying that there's no noticeable gas consumption difference between driving with your windows down and using your ac.
  • markp93, on 10/12/2007, -0/+18Mythbusters also blew apart the myth that driving with your truck's tailgate open will save gas, when according to their tests it actually decreased fuel economy. It seems that with the tailgate closed, any air that circulates directly behind the cab serves as a buffer for air passing overhead making the airflow more streamlined. With the tailgate open, air passing over the cab gets pushed into the bed of the truck, pushing it down and increasing drag.. something like that.
  • korashime2001, on 10/12/2007, -0/+17"* Removing excess weight from your car"

    Are you calling me fat?
  • iamnos, on 10/12/2007, -4/+20@geoken

    While what you say is true, the dyno's miss one thing when talking about most fuel efficient speed, and that is air resistance. Everything looks great in the shop when you're not actually driving 100+km/h. However, the faster you go, the more air resistance there is, and your fuel economy will drop. While its true that every vehicle is different, given the driving habits of most people, slowing down will increase fuel efficiency.
  • ohmar, on 10/12/2007, -2/+16Yeah, im sure the truckers REALLY appreciate having some dinky little car tailing him in the blind spot of his mirrors. Makes his job a lot easier. Especially when he has to slam on the breaks and you get sandwiched between him and the truck behind you.
  • sdfghjkl, on 10/12/2007, -2/+16Especially in older cars the AC will rob you of gas. There is a noticeable shift in power when I turn the AC on in my '96 Civic.
  • rollem, on 10/12/2007, -1/+14Actually, you have a good point. Having more traffic circles would cut the use of gasoline down to some extent. They would have to be very widespread in order to make much of a difference, but it might be significant.
  • HomerS1, on 10/12/2007, -3/+14True, using AC will consume more fuel than without. It is also true, however, that the fuel savings by driving w/o AC will be negligible.

    The impact on your interpersonal relationships with friends/family (due to your excessive BO from sweating like a pig in your car trying to save a penny) will far outweigh any real fuel savings.
  • pintong, on 10/12/2007, -0/+11"They left off tip #5: Drive _with_ the wind, never against it."

    That's a great tip. What's your advice on getting the wind to blow in the direction I'm going?
  • consoneo, on 10/12/2007, -7/+18@rollem I can drive 20 miles an hour in 5th gear on a flat surface... The engine is crying, but I can do it... you're saying that's my most fuel efficient?

    I beg to differ. It all has to do with load. The RPM does not equal the fuel usage. To ramp up RPM or get more power, you must squirt more fuel and more air into the combustion chamber. So if I have it floored in 5th gear at 20 miles an hour, I'm at max fuel consumption because the car is trying to increase RPMs as much as possible.

    It is my opinion, and experience (due to the fact that my car has a fuel monitor and shows the preceeding to be true), that the least amount of peddal depression is your optimum cruising speed in each gear.

    TADA! :)
  • tehgoatman, on 10/12/2007, -2/+13Removing excess weight from your car can also help save you gas. The Department of Energy estimates that drivers can save anywhere between 3 and 6 cents a gallon (assuming gas prices of $2.97 a gallon) just by removing those golf clubs and other unnecessary weight from your trunk.

    Whatcha gonna do with all that junk? All that junk inside your trunk?
  • BIllyBobFett, on 10/12/2007, -0/+9"Who the hell is 'they'?"
    I believe 'they' refers to gas additives, the nearest antecedent. That's the way English works.
  • fadetoone, on 10/12/2007, -4/+12My favorite is all those people that drive their pick-up trucks around with the tailgate down to save gas because it reduces drag, when in fact there's less drag with it closed.
  • Rikkochet, on 10/12/2007, -5/+13They did a Mythbusters episode on that and ran 2 identical SUVs around a track. One had the windows down and the other had the AC on.
    They drove until they were both out of gas - I believe the SUV running the AC dropped out 5 (or 50?) miles before the one with the windows down did.
  • i64X, on 10/12/2007, -0/+8The ones that get 55mpgs also do 0-60 in about 17 seconds. That wouldn't fly in the States.
  • EBFoxbat, on 10/12/2007, -5/+13Draft. Find a big truck and ride his ass! The decreased drag combined with the decreased speed which the right is certainly driving at will greatly improve your mileage.
  • vAlatalo, on 10/12/2007, -3/+11dayz

    Gas price is currently $6.72 / gallon in Finland (1.319 € / l)..
  • shieldsmw, on 10/12/2007, -0/+8Damn it, every summer people start arguing about all the ways you can save gas. Roll up your windows, remove excess weight... Among the tips, you never hear the obvious.

    DON'T DRIVE YOUR CAR. You'd be amazed how much gas you can save when your car is off.
  • mywhitenoise, on 10/12/2007, -3/+11Yeah, I'll ride my bike home, with 8 bags of groceries hanging on the handle bars. I'll spend 4 hours riding 20 miles to work, and another 4 hours riding home. I'll also bring along my friends on the pegs, or maybe I can get a side-cart.
  • rollem, on 10/12/2007, -0/+7Fadetoone is right. There actually is no aerodynamic advantage to driving with your tailgate down. The pocket created by the cab extends just a bit farther back than the tailgate, the open tailgate actually interferes with the air more than the closed gate.
  • 10lbhammer, on 10/12/2007, -0/+7I like to roll with my windows down blaring my baba o'reilly.



    it's just better.
  • HairyReasoner, on 10/12/2007, -0/+6Avoiding rapid starts and stops is a pretty important point from the article. Every time you use the brakes, you are wasting energy-- converting the chemical potential energy in the gasoline into useless heat.

    So, if you drive in such a way as to minimize the amount of braking you do, you'll save energy.
  • wyattearp, on 10/12/2007, -1/+7personally, i like 'ride the motorcycle that gets 55mpg' as an alternative to driving the car
  • superguysteve, on 10/12/2007, -0/+6Here's a gas saving tip:

    drive your Hummer off a ***** cliff and save some gas for the rest of us.
  • rollem, on 10/12/2007, -0/+6@luckyink - If a company found a magic additive that cut fuel consumption by 10%, don't you think they would advertise it? If you were convinced that this additive would really work, would you buy gas from them? That's how capitalism works. Of course, it relies on competition and if you believe that the big oil companies are really a monopoly, then your suggestion would be right. However, competition is in fact very strong between the oil companies, people go far out of their way just to save a few cents per gallon.
  • seether166, on 10/12/2007, -0/+6@geoken

    Did you RTFA? That is the myth they are trying to dispel. Whether or not I agree with it is one thing, but I bet you didn't even RTFA since you don't even address it in your comment.
  • twb010, on 10/12/2007, -2/+8They went back and retested that myth and found that driving with a mesh tailgate was the best option.
  • paulgifford, on 10/12/2007, -1/+7Windows down vs. air conditioning

    "Urban puzzle": it is more efficient, on a hot day, to run with the A/C on and windows up than to run with windows down (b/c of increasing car's drag).

    Computer-based mpg measurements:

    * 11.7/11.8 with A/C on and windows up
    * 11.7/11.8 with A/C off and windows up
    * 11.3 with A/C off and windows down

    So, according to the computer, it's better to use A/C with windows up.

    This was too quick and easy for TV, so they decided to stage a seven hour marathon, race-til-you're-empty duel, with Jamie driving an SUV with A/C on and Adam driving an SUV with windows down. Though, once the safety inspector intervened, it was no longer a seven-hour marathon, it was a bit slower (45mph instead of 55mph), and a lot shorter (only 5 gallons each).

    Jamie's A/C car ran out of gas first -- Adam's windows down SUV ran for another 30 laps -- completely contradicting the computer mpg estimate. Computer estimate based on air flow into the engine, so it would appear that it is unable to properly model the difference between A/C and windows down.

    Mythbusted
  • KnightMareInc, on 10/12/2007, -3/+8didnt mythbusters already do an episode about these?
  • inmatarian, on 10/12/2007, -2/+7The "Driving The Speed Limit" advice actually doesn't mean that driving at 55 is better than driving at 70. The advice should read "Drive a consistent speed." It just so happens that when you drive at the speed limit, you're driving at the speed that's the highest you can get on that particular road and remain consistent. Any higher and you'll find yourself hitting the brakes a lot to make turns, and wasting gas speeding back up to the higher speeds that you want, and thats where most of your fuel economy disappears to.

    Run an experiment. During city driving, stop trying to be the first person to the next stop-light. Cruise leisurely between lights, with a slow acceleration and slow braking, and you'll notice that you're getting better fuel economy.
  • 93ex, on 10/12/2007, -1/+6@elias1

    My Blazer gets better mileage at 65 mph, instead of the speed limit, which is 70 (on the interstate) I guess thats the threshold between gearing/power/aerodynmaics.
  • frostieDude, on 10/12/2007, -1/+6I find the best way to save gas is to ride my Vespa instead of driving my car as much as possible.
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