Yes, warming up your car before driving in cold weather can damage the engine over time

As winter approaches, many people are preparing their homes and vehicles for colder weather.

In frigid temperatures, it’s a common practice for many drivers to let their cars warm up for a while before they hit the road to keep themselves from freezing. Some vehicles even have a preset feature that lets drivers start their cars remotely.

Additionally, many also believe that a car needs to warm up to help its engine run more efficiently. But some people have said warming up your car before driving in cold weather could actually damage the engine. This prompted a VERIFY reader to ask whether that’s true.

One thing we want to note: Of course, you shouldn’t drive a car when it’s covered in snow or when you can’t see out of an ice-covered windshield. But when it comes to the idea that warming up your car helps it run better, we VERIFY whether that practice is helpful or if it could cause harm.   

THE QUESTION

Can warming up your car before driving in cold weather actually damage the engine?

THE SOURCES

• U.S. Department of Energy
• U.S. Environmental Protection Agency
• Utah Department of Environmental Quality
• Firestone Complete Auto Care
• Chuck's Auto Repair in Seattle, Washington
• Smart Motors Toyota in Madison, Wisconsin
• NAPA Auto Parts
• Consumer Reports
• Stephen Ciatti, Ph.D., principal engineer for battery systems at PACCAR Technical Center
• William Northrop, Ph.D., professor of mechanical engineering and director of the Thomas E. Murphy Engine Research Laboratory at the University of Minnesota
• Peter Zavarelli, automotive repair expert at JustAnswer

THE ANSWER

Yes, warming up your car before driving in cold weather can cause long-term damage to the engine due to excessive idling. Most vehicles built after 1980 no longer need to warm up before driving in the cold, and experts say slowly driving off about 30 seconds to a minute after starting your car is a best practice.

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WHAT WE FOUND

Although many people warm up their gas-powered vehicles in winter, all of our sources agree that excessive idling can cause damage to the engine over time.

“If you're one of the many drivers who thinks it’s important to turn on your car and let it sit for a bit before hitting the road in wintry weather, you could be doing your engine more harm than good,” Firestone Complete Auto Care says.

The Utah Department of Environmental Quality agrees.

“Excessive idling can actually damage your engine components, including cylinders, spark plugs, and exhaust systems,” the Utah DEQ says. “Many components of the vehicle — including the wheel bearings, tires and suspension system — will warm up only when the vehicle is moving. You need to idle no more than 30 seconds to get the oil circulating through the engine.”

Gas-powered cars need oil to keep their engines lubricated. When you start a car, an oil pump circulates the oil in less than a minute. Letting your car idle in cold temperatures can shorten the life of your engine by stripping away oil from the engine’s pistons and cylinders — two critical components that help your engine run, Stephen Ciatti, Ph.D., principal engineer for battery systems at PACCAR, told Business Insider in 2016.

“What happens when you turn an engine on or crank your engine over from cold is that it turns the crankshaft of the engine and makes the pistons go up and down, and some fuel needs to go inside the chamber in order for it to start to burn,” mechanical engineering professor William Northrop, Ph.D., told VERIFY.

Some people let their cars idle to warm up the interior, but “constantly letting a cold engine idle can actually be counterproductive because it gradually strips oil away from the engine’s pistons and cylinders,” according to Chuck’s Auto Repair.

“Here’s the problem: when the engine is cold, the gas may not evaporate completely as it combines with the air,” Chuck’s Auto Repair explains on its website. “For more recent cars with an electronic fuel injection, there are sensors that detect this and compensate by adding more gas to the mixture.”

“When there is excess fuel in the chamber, some of it condenses onto the cylinder walls and strips away the lubricating oil. When the lubricating oil is gone, components like the cylinder liners and piston rings will wear prematurely,” Chuck's Auto Repair says — and “less oil means more friction, more wear and tear, and a shorter life for your engine,” according to Firestone.

While some drivers let their cars idle to warm up the cabin, others may actually be trying to protect their engines because of outdated guidance.

Most cars made before 1980 did need to warm up when it was cold out, according to Firestone and Smart Motors Toyota. This is because older model cars had carburetors that regulated the air-fuel mixture within the engine and could not accurately adjust the air-to-fuel ratio in cold weather.

“In cold temperatures, carburetors couldn’t vaporize all the gasoline they let into the engine, so some of it would be left behind as a liquid rather than being burned off during combustion. In order to work properly, a carburetor needed to warm up or else you’d run the risk of stalling out,” Firestone says.

But technology has improved since the 1980s. Nowadays, the vast majority of cars sold in the U.S. have an electric fuel injection system that helps maintain the perfect air-fuel mixture needed for a combustion event, no matter the ambient temperature.

“Modern vehicles are really good at controlling how much fuel goes into the engine, and deciding how to do that under cold conditions,” Northrop says. “[They] don’t require warm up in order to run effectively or run smoothly, even in the wintertime.”

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Instead of waiting for your car to warm up when it’s cold outside, most manufacturers recommend driving off slowly after about 30 seconds because the engine warms up faster when the car is being driven, according to the U.S. Department of Energy.

“In general, the most that you should be warming up your car is 30 seconds, and most of the time, you don’t even need that much,” Northrop says.

If you have a lot of ice or snow on your windshield, Northrop recommends scraping it off with an ice scraper instead of letting your car idle for a long time while waiting for the defrost setting to kick in before driving off.

“You do definitely want to spend the time to clear the ice and snow off your vehicle before you drive because it can be very dangerous if you don’t have good visibility,” Northrop says.

“This means that your cold-day-driving routine should look something like this: bundle up, start the car, scrape the ice off the windows and mirrors, get in the car and get going!” Firestone says.

Just make sure you don’t accelerate too fast or rev your engine in the first few moments you start driving, Northrop and Smart Motors Toyota both say.

“This can add unwanted strain to your bearings and flood the combustion chamber with gas, which, in turn, will take miles off your engine’s life,” Smart Motors Toyota says.

For owners of electric vehicles, which don’t have traditional gas-powered engines, the above information doesn’t apply, according to a blog post on NAPA Auto Parts’ website. Instead, NAPA advises EV owners to warm up their cars before they’re unplugged because it can help preserve the battery range.

“EVs have to draw on electricity to warm the interior. If you enter a car with a cold cabin and begin driving, the vehicle will need to take from its stored electricity to bring the inside air to a pleasant temperature. This will tax the EV’s battery and leave you with less driving range,” NAPA says. 

This story is also available in Spanish / Lee este artículo también en español: Sí, calentar tu coche antes de conducir en clima frío puede dañar el motor con el tiempo