The Cold Truth About Warming Your Car Up in the Winter

Letting your car warm up for more than 30 seconds in cold weather wastes fuel, hurts the environment, and can damage your engine.
Written by Jason Tushinski
Edited by Pat Roache
Drivers should only heat up their car for a maximum of 30 seconds on an average winter day to minimize fuel waste, pollution, engine wear and tear, and window fog.
  • Modern engines use electronic fuel injection systems and multigrade engine oils that don’t need time to warm up at low temperatures—as low as -40° F.
  • Experts recommend driving your car gently for about 15 minutes to prime the engine in cold weather rather than letting it idle for too long.
  • Americans could cut down on $5.9 billion in fuel costs if everyone took steps to reduce their winter idling times.

The harmful effects of idling your car in winter weather

Letting your engine run for an extended period of time without driving hurts your wallet, the environment, and your car:
  • Idling wastes gas: Modern engines use electronic fuel injection systems to calculate how much gasoline and air are needed to
    start a cold engine
    . According to a cold-weather study by the Government of Canada, waiting five minutes for the engine to "warm up" could plummet your fuel economy by 7% to 14%, and ten minutes could drop your fuel efficiency by 12% to 19%.
  • Idling increases air pollution: A 2009 energy sector study found vehicle idling made up an astounding
    1.6% of U.S. greenhouse gas emissions
    , half of which came from cold weather idling. That figure is twice the number of emissions caused by the entire steel and iron manufacturing industry!
  • Idling harms your engine: The excess gasoline that accumulates in your engine’s gas-air mixture when you leave your car running can strip oils from the cylinder walls. This decreases engine lubrication, leading to more—and faster—
    wear and tear

Modern cars only need 30 seconds to warm up

According to the EPA, modern vehicles that are less than 30 years old won’t need more than:
  • 30 seconds to get their engine warm enough for a standard cold day.
  • One minute to get an engine to ideal operating temperature in exceptionally frgid weather.
What to do instead: Auto experts recommend warming up your engine for winter driving by driving gently for 15 minutes right away—not idling for a few minutes.

Common myths around warming up your car in winter

Cold engine myth: Cold weather slows gasoline’s evaporation, leading to condensation on the intake manifold’s walls and likelihood of a
stalled engine
Cold engine fact: While this is true of older cars that used carburetors to start a combustion engine, most new vehicles since the mid-1980s use electronic fuel injection systems that automatically regulate the gasoline needed to start a cold engine.
Engine oil myth: Your car’s engine oil needs time to warm up in winter weather so it can lubricate all your engine components properly. 
Engine oil fact: Most multigrade engine oils recommended by modern car manufacturers are engineered to work in low temperatures down to -40 degrees Fahrenheit from start-up.
Window fog myth: Your car needs to warm up to defog your car windows.
Window fog fact: Letting your car idle actually increases fog on your windshield, since moisture typically finds the coldest place to settle—your car windows! Here’s a trick you can try to defrost foggy windows:
  • Turn on your car’s defogger to start clearing your windows.
  • Now, turn your car’s heater to high to warm up the air inside your car.
  • Then, turn your air conditioner on high to pull in any extra moisture in the air.
  • Next, turn all air circulation off.
  • Open windows slightly to allow fresh air in.

The advantages of cutting down on idle time

A 2009 study from the Department of Energy concludes that:
  • Cutting unnecessary idling could
    save Americans $5.9 billion on fuel costs
  • The amount of emissions saved by widespread idling cuts would dwarf the emissions of the aluminum, soda ash, and limestone industries put together.
Legal consequences: Some municipalities—such as frigid
—have instituted heavy fines for idling more than a set amount of time each month.
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The EPA recommends that drivers should restrict their cold weather idling time to no longer than 30 seconds (or a minute on really cold days). Instead, experts recommend gently driving for about 15 minutes to get your car’s engine temperature up to its optimal performance levels.
Yes: When your fuel injection system pumps too much gasoline into an idled engine, the excess gas can strip your engine of the oils it needs to operate properly. This can accelerate wear and tear on your engine.
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