Why you shouldn’t warm up your car in winter

On a cold morning, the last thing you want to do before heading off to work or run errands is to emerge from the cozy warmth of your home to the arctic chill of your driver’s seat.

For decades, the common wisdom has been that the best way to avoid this finger-numbing scenario is to let your vehicle idle for a while, so that both its interior and engine have a chance to “warm up.”

But if you’ve been relying on the long-held myth that letting your car idle in cold weather is a smart way to extend the life of your engine, we’ve got bad news for you: it’s doing just the opposite (at least for gasoline engines).

In a conversation with Business Insider, Stephen Ciatti — who spent more than 16 years as the principal mechanical engineer at the Argonne National Laboratory, the U.S. Department of Energy’s science and engineering research center — said that in addition to wasting fuel, letting your car warm up in cold weather also strips your cylinders and pistons, two of the key components that help the engine run, of much-needed oil. 

Normally, Ciatti explained, a car’s engine runs on a mixture of air and vaporized gasoline. But when the temperature drops, the gasoline has a tougher time evaporating, so your engine ends up using more gasoline. 

“That’s a problem because you’re actually putting extra fuel into the combustion chamber to make it burn and some of it can get onto the cylinder walls,” Ciatti told Business Insider.

“Gasoline is an outstanding solvent and it can actually wash oil off the walls if you run it in those cold idle conditions for an extended period of time.”

If you warm up your car as part of your regular routine, that washing “can have a detrimental effect on the lubrication and life of things like piston rings and cylinder liners,” which are critical engine components.

A better way

But that doesn’t mean that you should hop into the driver’s seat, rev up the engine, and peel out of the driveway, either. According to Popular Mechanics, “It takes five to 15 minutes for your engine to warm up while driving, so take it nice and easy for the first part of your drive.”

Their suggestion? If it’s cold and icy, turn on the car and your defroster, then spend a minute or so scraping your windshield. That should be enough time to get the temperature a little more comfortable — and to get you where you need to go, safely.