Here’s Why You Shouldn’t Warm Up Your Car In the Winter

I’ve spent many mornings tromping out in the snow to start my car, before going back inside to finish breakfast. With my old ’81 Subaru, warming up my car by idling it in the winter helped the engine survive more than 300,000 miles. But with my ’08, everything after the first minute or so is a waste of gas.

That’s because modern engines are designed to operate efficiently without extended warm-up periods, says Justin Dugan at American Trucks. “A common misconception is that idling helps the car warm up faster, but idling only minimally raises the engine temperature while still consuming fuel,” he says. “Driving at moderate speeds actually warms the engine more effectively.”

But, that doesn’t mean warming up the car on a cold day is a wholly bad idea. “It is good for the engine and transmission to be at least a little warm before traveling, and it makes you more comfortable inside the car, which also keeps you ready and alert,” says Chris Pyle, an auto expert with JustAnswer.com.

Does Warming Up the Car While It Idles Damage It?

No, warming up your car in winter by letting it idle will not damage it. Neither will not warming it up, as modern engines are designed to be driven even when they’re cold.

You could call this a car myth. The only exception is if your car is over 30 years old (give or take, depending on the model). In that case, not letting it warm up fully can cause excessive wear to bearings, piston rings and other engine parts.

Whatever the age of your car, if you do warm it up, don’t let it idle for more than ten or 15 minutes, says Pyle, since that’s a waste of fuel, causes pollution and can be dangerous to your health. “If it idles too long, it can cause excessive emissions, which can result in carbon monoxide poisoning in your home if the car is in the garage,” he says.

Should I Warm Up My Car in the Winter?

It depends. If you have an old car with a carburetor or early fuel-injection system, you should always warm it up before driving to ensure the oil has circulated through the engine and to avoid burning excess fuel.

Modern engines, however, don’t need to be fully warmed up before driving. Their fuel systems can also optimize fuel delivery when cold. However, it’s still a good idea to let them idle for 30 seconds to a minute.

“After that point your engine is fully lubricated with oil and ready to go,” says Duane “Doc” Watson, a technical trainer at Bosch Mobility Aftermarket. “It’ll still have some warming up to do before it reaches its peak operating temperature, but most of that temperature increase comes with driving.”

It is also beneficial to warm up modern cars in winter before driving them to allow windows to defrost and the cabin to warm up. But keep in mind that extended idling contributes to air pollution, and leaving your car unattended with the key in the ignition encourages theft.

“I would recommend you sit in the car or clean the windows off while warming up,” says Pyle. Also, “revving the engine some will result in the coolant getting hotter sooner, but it is not a night and day difference. Just let it idle, the heat will start rolling soon enough.”

Regardless of how long you warm up your car, to avoid unnecessary stress on it, take it easy with acceleration for the first 10 minutes or until the temperature gauge moves away from the coldest side, says Watson. And if you do let your engine idle for long periods, remember that will decrease the time needed between oil changes.

Alternatives to Warming Up Your Car Before Driving

Reduce the need for idling on a cold day by:

• Use a block heater plugged in two hours prior to traveling
• Park in a garage or covered carport
• Place cardboard over your windows to prevent snow and ice accumulation

FAQ

Is It Bad to Run the AC When the Car Is Idling?

Not really. While the AC compressor does put extra strain on the engine, it’s not overly harmful to it. However, the engine will consume more fuel when the AC compressor is on, so “It’s mainly a fuel efficiency issue, leaving the choice up to the driver,” says Dugan.

Stay Warm While Driving This Winter

If your car heater’s acting up this winter, you’re not alone—here’s how to troubleshoot common problems and stay warm on chilly drives.

• Creative Ways to Stay Warm In a Car That Has No Heat
• If Your Car Has No Heat, This Is What It Could Mean
• What to Do When Your Car Heater Won’t Work
• Best-Rated Portable Auto Heaters for Comfortable Winter Driving
• If You Live In These States, Warming Up Your Car Is Illegal
• Car Cabin Air Filter Replacement
• Blower Motor Replacement

About the Experts

• Duane “Doc” Watson is a technical trainer at Bosch Mobility Aftermarket. He has more than 45 years of experience in automotive repair, has trained thousands of technicians and earned many industry awards, including Chevrolet Technician of the Year and Buick Service Master of the Year.
• Chris “Moose” Pyle is a master-certified technician with 20-plus years of automotive experience. He has also worked as an expert for JustAnswer.com since 2006, where he answers hundreds of car maintenance and repair questions a day.
• Justin Dugan is a brand ambassador at American Trucks and has worked as an automotive writer and TV host since 2011.