Gas-Saving Tips: Fact or Fiction?

Driving with air conditioning, cleaning your air filters, gassing up in the morning, using premium fuel all improve fuel efficiency — or do they? Rik Paul, automotive editor for Consumer Reports talks with Michele Norris about tests that dispel popular myths about fuel efficiency.

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ROBERT SIEGEL, host:

As prices at the fuel pumps continue to rise, folks are looking for ways to save on gasoline. On the Internet and on television, there is no shortage of tips.

(Soundbite of montage)

Unidentified Man #1: Changing your filter can definitely save gas.

Unidentified Man #2: Best time of day to fill up is in the early morning...

Unidentified Man #3: ...the air conditioner won't have to work as hard and you'll save gasoline.

MICHELE NORRIS, host:

Well, to find out what does or does not work, we turn to Rik Paul. He's the automotive editor for Consumer Reports, and he joins us now from Yonkers, New York.

Welcome to the program.

Mr. RIK PAUL (Consumer Reports): Hi, Michele.

NORRIS: Well, we thought you could help us bust some of the gas saving myths that are out there. And we have a list we'd like to tick through. Could we start with what we'll call myth one. You actually get better gas mileage if you don't run your air conditioning?

Mr. PAUL: You actually lose about a mile per gallon if you run your air conditioning. But to us, that's a good trade-off because air conditioning, if you need it, can really keep a driver alert and focused and relaxed and help him be a safer driver. Now, if you turn off your air conditioning and put down the windows on the highway, you're also going to lose about a mile per gallon, so it's a wash.

NORRIS: But why do you lose if you roll down your windows? Is that drag or something like that?

Mr. PAUL: Exactly, it disturbs the aerodynamic drag of the car.

NORRIS: Let's move on to myth two. A clean air filter will get you better mileage, true or false?

Mr. PAUL: False, according to our tests. We put a clogged air filter into a Camry and a Mercury Mountaineer SUV, and neither one lost fuel economy because of it. And the reason is modern engines automatically compensate for that by reducing the gas going in to match the reduced air.

What we did find is that you get less power, so we had poorer acceleration but the fuel economy was the same.

NORRIS: Rick, let's briefly deal with a few myths that are associated with gas. For instance, is it better to gas up in the morning?

Mr. PAUL: Not according to our tests. I know that lot of people say gas up in the morning when the air is cool, because when its hot in the afternoon the gas has expanded and you're getting fewer gas molecules for every gallon you pump.

But in our tests, we found that the temperature of the gas coming out the pump varies very little between morning and afternoon. And that's because most gas stations keep their gas storage tank underground, where the temperature variation is much less than in the air.

NORRIS: It is better to use premium gas? Does that give you better gas mileage?

Mr. PAUL: Most cars are designed to run just fine on regular gas, and so if you put premium into them, you're not going to get any better performance, fuel economy, anything except you're going to pay 20 cents more per gallon.

NORRIS: How about starting your engine and letting it idle a bit before you actually take off and drive?

Mr. PAUL: Well, I think that's something that a lot us of where told by our dad when we where learning to drive, but with modern engines they don't required a warm-up period. In fact, what you want to do is you want to get up to operating temperature as quickly as possible, because that's where an engines is most efficient. And so if get in, turn it on and start driving, you're actually going to warm up the car faster than if you sit and let it idle. And when your idling, you're getting zero miles per gallon.

NORRIS: So it's a case where dad didn't always know best.

(Soundbite of laughs)

Mr. PAUL: I think technology has changed.

NORRIS: So, we've ticked through some of the myths. How about some actual good advice for saving on gas?

Mr. PAUL: Well, if you're driving on the highway, the best thing you can do is watch your speed. We measured a Toyota Camry at 55, 65, and 75 miles per hour and found that when we went to 65 from 55, we lost five miles per gallon, and when we went up to 75, we lost another five miles per gallon. If you have the patience, you have the time, slow down, take your time - you'll save some money. Of course the most effective way to cut usage is to buy a more fuel-efficient car.

NORRIS: Oh yes, there's that too. Rik Paul is the automotive editor for Consumer Reports. He joined us from New York.

Thanks so much, Rik. Drive safely.

Mr. PAUL: Thanks, you too.

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