4 gas-saving myths

[one...two...tree 2,762]

By David Ellis, CNNMoney.com staff writer

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.

Right now, the price of gasoline is again setting record highs. The average price for a gallon of regular hit $3.087 Tuesday, the third record in a row.

So before you attempt a half-baked scheme to stretch your gas dollars, here's a look at what's fact and what's fiction when it comes to fuel economy:

Nothing but gimmicks

There have been additives, special magnets and even a pill that has promised to improve a car's fuel efficiency by as much as 30 percent in some cases.

While the promise of stretching your gas dollars seems awfully lucrative, especially when they cost under $20, most of these products provide a negligible, if any, improvement in fuel efficiency, said Rik Paul, the automotive editor for the publication Consumer Reports.

Consumer Reports and the government's Environmental Protection Agency, have tested dozens of these products finding that none of them offer any significant improvement in fuel economy.

"With all the pressure car companies are under, if one of these inexpensive devices dramatically did improve fuel economy, they (automakers) would be all over it," said Paul.

Windows, air conditioning - who cares?

There's the old saw that leaving your windows rolled down creates an aerodynamic drag on your car, cutting down on fuel efficiency. And there's the notion that the fastest way to drain your gas tank is by running your air conditioning.

Don't believe either one.

In two separate studies conducted in 2005, the automotive Web site Edmunds.com and Consumer Reports compared the fuel economy of both a sedan and an SUV at highway speeds with and without air conditioning and how open windows affected gas usage.

What they found was no significant difference in fuel economy in either sedan or SUV under either condition.

Don't wait until Wednesday

Some drivers insist the best time to buy gasoline is on a Wednesday, when pump prices have cooled from the weekend run-up when oil companies typically raise prices.

That's true to a point, says Tom Kloza, chief oil analyst at the Oil Price Information Service. Gas prices tend to be higher on the weekend, but there's no ideal day of the week to purchase your gas.

Geoff Sundstrom of the motorist organization AAA notes that gas prices fluctuate from day to day and are determined by gas station owners who look at a variety of factors including wholesale gasoline prices, competitors' prices and food and drink sales if they have an attached convenience store.

Drivers who want to bargain-hunt for inexpensive gas should instead check out Web sites like Gasbuddy.com, which allows consumers to find the cheapest gas in their area simply by entering their zip code.

Restart your engines

It's probably a myth that goes back to the days when cars were equipped with carburetors, but many drivers believe that starting up and turning off your car repeatedly is a fast way to drain your gas tank.

But because of modern fuel-injection technology, drivers actually save gas by turning off their engine than letting their car needlessly idle, says Consumer Reports' Paul.

Granted it's probably not sensible shutting down the engine every time you get stuck in traffic, but if it looks like you might be at the drive-thru for more than 30 seconds to a minute, it's worth turning off your car, says Paul.

Tips you can use

So what are some fuel-savings tips you can trust?

Make sure your tires are properly inflated for starters. Besides posing a safety hazard, underinflated tires can reduce your fuel economy slightly, based on Edmunds.com's 2005 study.

Removing 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.

If your car comes equipped with cruise control, make sure you use it, especially on long trips. Edmunds.com's study revealed that using cruise control at highway speeds offered an average fuel economy savings of 7 percent.

But the biggest fuel saver is driving the speed limit and driving sensibly. Rapid starts and stops and exceeding the speed limit will dent your pocketbook. Just by adhering to one of those, the Department of Energy estimates that drivers can save anywhere between 15 and 98 cents a gallon, again assuming pump prices are at $2.97 a gallon.

[mawilson 2,133]

cutting off your A/C won't really cut your gasoline consumption.

You have got to be kidding me. When A/C is on, my car consumes 20-30% more gas (tested.)

[one...two...tree 2,762]

cutting off your A/C won't really cut your gasoline consumption.

You have got to be kidding me. When A/C is on, my car consumes 20-30% more gas (tested.)

Should've bought a Honda. j/k

Hmmm...I know that Mythbusters also tested this myth and it got busted. What kind of car you got?

[mawilson 2,133]

What kind of car you got?

A good ol' American muscle car -- the smallest possible car with the largest possible

displacement engine (6L V8, 400hp)

[Fandango 1,439]

I got a hoopty to run around town with when I'm not working...looks likea POS but deffo better mileage

[one...two...tree 2,762]

What kind of car you got?

A good ol' American muscle car -- the smallest possible car with the largest possible

displacement engine (6L V8, 400hp)

...and you see a dip in your fuel efficiency when you flip the A/C on? :oh:

[peejay 327]

But the biggest fuel saver is driving the speed limit and driving sensibly. Rapid starts and stops and exceeding the speed limit will dent your pocketbook. Just by adhering to one of those, the Department of Energy estimates that drivers can save anywhere between 15 and 98 cents a gallon, again assuming pump prices are at $2.97 a gallon.

We have a 2004 Honda Civic sedan and I get several more miles per gallon when I drive it than my wife does. I've been driving for 36 years and my wife just started driving 2 1/2 years ago. She has some really bad driving habits that I have tried to teach her to correct, but she is stubborn and still drives with a heavy foot in the gas and brakes. I've learned to brace myself when she is driving. I tell her frequently, "Cool it...you're scaring the sh*t out of me!"

Gas is still cheaper than a divorce. Better to keep my mouth shut most of the time (except in emergency situations).

Edited May 16, 2007 by peejay

[one...two...tree 2,762]

Gas is still cheaper than a divorce. Better to keep my mouth shut most of the time (except in emergency situations).

True wisdom right there.

[Ban Hammer 13,337]

cutting off your A/C won't really cut your gasoline consumption.

You have got to be kidding me. When A/C is on, my car consumes 20-30% more gas (tested.)

i feel the compressor kick on when i turn on the ac, no matter what size engine.

one way to save gas is to coast downhill if you have a stick

[mawilson 2,133]

What kind of car you got?

A good ol' American muscle car -- the smallest possible car with the largest possible

displacement engine (6L V8, 400hp)

...and you see a dip in your fuel efficiency when you flip the A/C on? :oh:

Yeah - it goes from 14mpg to 10

[Portlander 0]

I like to drive "sensibly", and in her VW Dasher I get 45 mpg compared to her lead-footed 40 mpg

Re: A/C ... if the A/C is on while you are on the freeway, of course there is going to no effect. However, if you are city driving there will be a big effect. The A/C sucks a lot of power and, unless you are moving fast enough to create enough excess power to run the A/C, then you will burn extra gas to run the A/C. This is probably much less true in newer cars than in older ones, though...

hahahaha... saw this comment on another board and thought it was funny, and on subject...

Gee, nothing about buying a vehicle to match the task at hand. I have a co-worker who drives a daily 75 mile round trip commute using a 13 mpg full-size pickup truck. He don't carpool, either. Considering how much he spends on gas right now, he could park the truck, buy a Toyota Yaris for $11K, and have enough money left over in a year for ####### extension surgery.

[Saddle Bronc 124]

Plus, the effect of windows vs. AC.

For non-convertible post-1960 cars, open windows DO cause quite substantially higher drag @ freeway speeds--which can offset the weight (and power draw) of the AC. Vents alone (windows closed)--may optimise fuel economy^* at the cost of some comfort

^*I have not actually tested the fuel economy, though I have driven in no-AC car at freeway speeds in Alberta. Little effect on comfort THERE (as temps rarely climb above 30^oC/86^oF), but vents-only is quite uncomfortable in Atlanta, Dallas, Memphis...or even DC/Balto.

[Niels Bohr 72]

cutting off your A/C won't really cut your gasoline consumption.

You have got to be kidding me. When A/C is on, my car consumes 20-30% more gas (tested.)

Consumer Reports is not a scientific magazine but a business magazine. You're right, A/C increases load on a car because it produces more heat to drive more cold air into the car. Therefore, the efficiency drops about 20%.

Basic physics shows that the heavier the mass of an object the more energy it needs to push the object. The writer knows this, but, don't know the rest of the story on cars. Aerodynamic on cars uses Bernouli's principle, "Fast moving fluid exerts less pressure." Less pressure equals more efficiency. Rolling down a window may sometimes cause the car to reduce in efficiency by as much as 5%. There's a reason why a semi have that round curved object above its top (roof).

If you are stopped for more than 1 minute, turn off the engine. It takes less energy to start up the engine than it is to have the car running idle for more than one minute.

If you are close to exit slow down and don't accelerate the car anymore. This will decrease the amount of energy used by the car, instead of a quick increase in speed and then hitting the brakes. All of those energy is converted to heat. It's good if you have a hybrid, but, not good with gasoline car.

I drive on the highway, and I am surprised as to how many imbeciles drive. Well, they are just that, imbeciles trying to push me off from my lane because I was basically doing my best to keep my gas mileage high. Tailgating me thinking that I would budge. I don't budge for any morons. They can move or we can both die if I hit the brakes, as long as I am efficient.

[almaty 19]

cutting off your A/C won't really cut your gasoline consumption.

You have got to be kidding me. When A/C is on, my car consumes 20-30% more gas (tested.)

Consumer Reports is not a scientific magazine but a business magazine. You're right, A/C increases load on a car because it produces more heat to drive more cold air into the car. Therefore, the efficiency drops about 20%.

Basic physics shows that the heavier the mass of an object the more energy it needs to push the object. The writer knows this, but, don't know the rest of the story on cars. Aerodynamic on cars uses Bernouli's principle, "Fast moving fluid exerts less pressure." Less pressure equals more efficiency. Rolling down a window may sometimes cause the car to reduce in efficiency by as much as 5%. There's a reason why a semi have that round curved object above its top (roof).

If you are stopped for more than 1 minute, turn off the engine. It takes less energy to start up the engine than it is to have the car running idle for more than one minute.

If you are close to exit slow down and don't accelerate the car anymore. This will decrease the amount of energy used by the car, instead of a quick increase in speed and then hitting the brakes. All of those energy is converted to heat. It's good if you have a hybrid, but, not good with gasoline car.

I drive on the highway, and I am surprised as to how many imbeciles drive. Well, they are just that, imbeciles trying to push me off from my lane because I was basically doing my best to keep my gas mileage high. Tailgating me thinking that I would budge. I don't budge for any morons. They can move or we can both die if I hit the brakes, as long as I am efficient.

good post brother console..thanks

[homesick_american 1]

cutting off your A/C won't really cut your gasoline consumption.

You have got to be kidding me. When A/C is on, my car consumes 20-30% more gas (tested.)

Should've bought a Honda. j/k

Hmmm...I know that Mythbusters also tested this myth and it got busted. What kind of car you got?

I seem to recall them re-doing it and confirming it. I love that show. Adam is a sex beast.