Dear Car Talk:

When my sister and I shop, we save time by having lunch in the car. When she drives, if it is winter or summer, she will leave the car running for the half hour we eat, so she can run the heat or air conditioning. When I drive, I think that practice is not good for the car, so we suffer with the motor off.

Is it acceptable to idle the car so we are comfortable? Thank you. — Annette

Idling doesn’t harm the car at all, Annette. If your sister starts idling near the mall, that’s another issue. But idling is no problem for your engine.

As long as your cooling system is working (and you’d know if it wasn’t because you’d see a “HOT” warning light on the dashboard), cars can idle indefinitely. Or until they run out of gas.

Idling is actually easier on the car than driving. The engine is doing very little work. I guess that’s why they call it idling.

But there are two concerns, and they’re related. One is pollution. When you sit there idling, the engine is still putting out carbon monoxide, carbon dioxide, unburned hydrocarbons and nitrous oxide compounds.

And because of that pollution, the second concern is that many towns and cities now have anti-idling ordinances. Those limit the amount of time you can legally let a vehicle idle without shutting it off. So check your local regulations.

That said, if your teeth are chattering, or sweat is dripping off your chin onto your fish tacos, there’s no reason to suffer. You don’t want to be wasteful, but you also don’t want to end up with frost bite or heat stroke.

So the real question is: Is there room for compromise, especially when the weather is more moderate?

If it’s, say, 80 degrees out, you can idle the car and run the AC for five minutes and then shut it off until you feel uncomfortably warm again. Or you can open the windows from the outset and run the blower fan without the AC in the car’s battery mode.

And if it’s 50 degrees out, you can run the engine and the heater until you’re toasty and then shut it off until you need some more heat. And on days when the weather is more extreme — here’s an idea — you can go into a restaurant, live it up, and use the bathroom, too.

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Got a question about cars? Write to Ray in care of King Features, 628 Virginia Drive, Orlando, FL 32803, or email by visiting the Car Talk website at www.cartalk.com.

© 2021 by Ray Magliozzi and Doug Berman

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