Why you shouldn't 'warm up' your car engine in cold weather?

Some experts say that warming up your car engine on a cold day is one of the biggest misconceptions about winter driving and can cost you a lot of time.

Why you shouldn't 'warm up' your car engine in cold weather? Picture 1

When the inside of your car is no warmer than the freezing outside environment, it's easy to believe that you need to let the engine warm up for a minute or two by idling before driving.

Giving your engine time to reach normal operating temperature makes it easier for your car to start than hitting the gas as soon as you turn the ignition on. A 2009 study found that, on average, Americans believe that car engines should be left idling for nearly four minutes in subfreezing temperatures—but the reality is, this move is bad not only for your wallet and the environment, but also for your car.

In 2016, Business Insider spoke with former drag racer Stephen Ciatti to get to the bottom of this popular myth. Ciatti has a PhD in mechanical engineering from the University of Wisconsin-Madison and has worked with internal combustion engines for nearly 30 years, so he has some knowledge about how to best care for a car in the cold. According to Ciatti, idling in cold weather will only shorten the life of your engine .

Why you shouldn't 'warm up' your car engine in cold weather? Picture 2

In older cars that used carburetors, cold weather actually posed a threat to engine performance. Gasoline is less likely to vaporize in cold temperatures, which prevents the carburetor from delivering the proper mixture of air and fuel to the engine. This can sometimes cause the vehicle to stall, which is why many people think it's necessary to warm up their car in the winter.

But if you're driving a car made in the last few decades, this isn't a concern anymore. Starting in the 1980s, car companies began replacing carburetors with electronic fuel injection systems, which use sensors to calculate the exact mixture of air and fuel to deliver to your engine.

When temperatures drop below freezing, your engine senses this and adjusts by introducing more gasoline into the fuel mix. By idling, you are exposing your engine to more gasoline-rich fuel than it needs, and this strips oil from vital engine parts.

Why you shouldn't 'warm up' your car engine in cold weather? Picture 3

" Gasoline is a great solvent, and it can actually wash oil off the [combustion chamber] walls if you run it in cold idle for long periods of time ," Ciatti told Business Insider. He said this washing action can eventually " have a detrimental effect on the lubrication and longevity of components like piston rings and cylinder liners ." So, in the end, what you intended to do gently to your car's engine could end up doing the opposite.

Once your engine reaches about 40 degrees, it will switch back to its normal fuel mixture, but idling won't help it get there any faster. The quickest way to warm up your engine is to drive it normally , says Ciatti . But don't use that as an excuse to pull into the driveway: It will take your engine five to 15 minutes to reach normal temperature from the moment you hit the gas. Until then, keep your foot on the gas pedal lightly to avoid putting any extra stress on the engine.

David Pac

Update 11 January 2025