You Don't Need to Warm Up Your Car, Regardless of the Weather

If you've ever borrowed your brother's car on a cold winter day, he might've sternly requested for you to let the car engine idle for at least five minutes before driving to school. But is this advice valid? Nope — not anymore, that is.

But Wait, Why?

In a 2009 study of costly myths, researchers found that Americans thought they should idle their cars (that's running the engine without actually going anywhere) for at least five minutes before driving when temperatures were below freezing. False! While it's true that cars are at least 12 percent less fuel-efficient in the winter, and it does take longer for the engine to heat up in those conditions, that doesn't mean you need to idle your car. The last time it was necessary was during the 1980s and early 1990s, when older cars relied on carburetors. A carburetor's job is to mix the right amount of gasoline with air for the engine to run properly, and it needs to warm up to do that properly. Otherwise, the car will stall.

Carburetors became obsolete once electronic fuel injection systems were introduced to the car industry. These modern systems rely on sensors, which monitor and adjust to the current temperature conditions in order to get the right air and fuel mix to the engine. No idling necessary.

Busting Winter Motor Myths

So, basically, if you drive a modern car, idling offers you zero benefits. The Environmental Protection Agency and Energy Department point out that most auto manufacturers only recommend running the car for 30 seconds before driving. Driving will warm up the engine faster than idling, anyway.

Plus, every minute you idle your car, you're just wasting fuel and contributing to greenhouse gas emissions. In an experiment performed by Natural Resources Canada, researchers found that total fuel consumption increased by 7 to 14 percent with a 5-minute warm-up and by 12 to 19 percent with a 10-minute warm-up.

That brings us to another popular car myth: the idea that starting your car wastes more gasoline than idling does. After all, it's cold out there! Who wants to turn off that toasty heater while you wait for a friend to finish at the post office? But the truth is that it's almost always more efficient to turn your car off than it is to keep it running. According to the Hinkle Charitable Foundation, idling for any longer than 10 seconds uses more fuel than it takes to start the car.

Not only is idling an environmental no-no, but it turns out that, depending on where you live, it might also be illegal. In Ohio, for example, idling your car at any time is strictly forbidden. The engine anti-idling law in Washington, D.C. states that: "Motor vehicles powered by gasoline or diesel are not allowed to idle for more than three minutes while the vehicle is parked, stopped or standing." (When temps drop below freezing, the grace period extends to five minutes.)

Wondering if you can legally idle? Look up your home state on the EPA's anti-idling regulations.

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Written by Anna Todd December 28, 2016

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