To Idle or Not To Idle?

Car exhaust on a cold day
Car exhaust on a cold day | Image by Arzu Kerimli/Shutterstock

With colder weather on the horizon, now is a good time to take another look at the century-old question of whether one should warm up their car before driving it in cold temperatures.

Back when cars had carburetors, the answer to that question would have been “yes.” The carburetor was used in gasoline-powered internal combustion engines to control and mix air and fuel entering the engine. However, that process did not work as well during colder 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,” a representative from Firestone told WFAA.

However, in the 1980s, automakers began manufacturing gas-powered vehicles with electric fuel injection systems instead of carburetors. The fuel injection systems can maintain the correct air-fuel mixture needed for combustion, regardless of the outdoor air temperature.

“Modern vehicles are really good at controlling how much fuel goes into the engine and deciding how to do that under cold conditions,” said William Northrop, a professor of mechanical engineering at the University of Minnesota, per WFAA. “[They] don’t require warm up in order to run effectively or run smoothly, even in the wintertime.”

Car care experts say excessively idling your car before driving can damage the engine over time.

“Excessive idling can actually damage your engine components, including cylinders, spark plugs, and exhaust systems,” the Utah Department of Environmental Quality explains on its website. “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.”

Chuck’s Auto Repair agrees, stating, “Constantly letting a cold engine idle can actually be counter-productive because it gradually strips oil away from the engine’s pistons and cylinders.”

“Less oil means friction, more wear and tear, and a shorter life for your engine,” the Firestone representative added, speaking with WFAA.

Therefore, it is not advisable to idle cars at length to melt off ice and snow that may have accumulated on the windshield. Instead, using an ice scraper to clear the windshield before starting the vehicle is better.

Of course, electric vehicles (EVs) do not have traditional gas-powered engines, so the information above does not apply. However, EV owners who wish to idle their cars to warm the interior of their vehicles should do so before unplugging to help preserve 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,” a NAPA Auto Parts representative explained to WFAA.

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