Better to let an engine idle on cold mornings, or to drive it right away?

Dear Car Talk

Dear Car Talk | Jan 01, 1996

Dear Tom and Ray:

We have a marital dispute and need your help in settling it. My wife and I have a running disagreement over whether it's better to let the car idle for a few minutes after starting it in cold weather or to begin operating it immediately. My wife has spent several years in northern climates, including Minneapolis. She contends that the car will stall unless it is allowed to warm up. I (who have never lived outside the confines of the sunny south) contend that the best thing to do is to get moving as soon as possible Who is correct?
Marshall and Lana

RAY: What a convivial confluence of connubial conditions. You're both correct!

TOM: In places like Minneapolis, where the label on your long underwear freezes to the top part of your butt in the winter, it makes sense to let the car idle for a minute or two. In sub-freezing temperatures, an engine may stall unless it's given an opportunity to run briefly before you impose a load on it.

RAY: But in more southern climates (like Iowa, for example) warming up the car may not be necessary. And in fact, all you're doing when you warm it up under those conditions is wasting gasoline and creating pollution.

TOM: So how do you know when your car needs to be warmed up? The car will tell you. If it stalls, it needs to be warmed up.

RAY: If you can drive away without stalling, then no warm up is required. And in fact, the best way to fully "warm up" the engine is by driving the car gently for five to ten minutes.

TOM: Most cars, in above-freezing temperatures, shouldn't need any time to warm up. So if it's above 32 F and your car stalls when you try to drive away, you may have some other problem, and it's probably worth getting the car checked out.

RAY: And by the way Marshall and Lana, congratulations! You're the first marriage this week we HAVEN'T broken up.

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