Idling for long periods might not damage your car -- but there are other reasons why it's a lousy idea.

Dear Car Talk

Dear Car Talk | Jul 01, 2007

Dear Tom and Ray:

I heard a caller on your show describe sitting in her car for 20 minutes while it idled so she could run her air conditioner and listen to her stereo. I couldn't have been the only one who cringed at that, could I? She was wasting money and fuel, generating pollution and, from what I've read, damaging her engine. Do you guys agree with this? -- John

RAY: We've never condoned excessive idling, John. Except in the case of my brother.

TOM: Right. Sitting on a park bench with a cup of coffee during working hours is great, and I highly recommend it.

RAY: But as far as cars are concerned, you're right on three of your four points: It does waste money, it wastes fuel and it creates more pollution. But it doesn't really harm the car.

TOM: Right. With modern, fuel-injected engines and with computerized engine management, the fuel is metered precisely enough that excess fuel isn't pouring into the cylinders, like it was in the old days of carburetors.

RAY: Nonetheless, idling is still wasteful and selfish, and bad for the planet. So we recommend that if you're going to be stopped for more than a few minutes, you turn off your engine.

TOM: There's no harm in turning it off and on again. There's no truth to the myth that you "use more gas starting it than by letting it run." And you can listen to your car radio with the key in the accessory position.

RAY: One of the ways hybrid vehicles save fuel is by automatically turning off the engine whenever you come to a complete stop, even at traffic lights. And my guess is that sooner rather than later, all new vehicles will adopt this "automatic stop-start" technology. It's an easy and relatively inexpensive way to cut our national gasoline use by probably 10 percent, and make intersections smell a lot better.

TOM: But you can contribute today, even if you don't have that technology, just by being conscious of when your car is stopped for a few minutes. When it is, shut off the engine. Future generations -- and the poor guy sitting behind you -- will thank you.

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