As temperatures drop, drivers let their car idle to warm up the engine and car interior. Experts weigh in on whether this type of idling does more good than bad for your vehicle.

Car Idling

Winter is in full swing, and folks that live in cold and snowy places often will leave their engine on in the morning to warm up the car before they start driving. In the past, this method was considered the safest way to ensure your car is warmed up and will run optimally. In fact, The Washington Post reported that a 2009 study found that “on average, Americans thought they should idle for 5 minutes before driving when temperatures were below 32 degrees.” But is this method still advised?

Well, it depends on how long you’re idling.

Some idling isn’t completely frowned upon, because cars do get less efficient in lower temperatures. explains in a recent article that when temperatures drop below zero, a car battery’s starting power can drop by as much as 50%. The Washington Post also stated that cars are at least 12% less fuel efficient in the winter. So a little bit of idling helps warm up the vehicle’s fluids, such as anti-freeze and brake fluid, which can help the car run optimally. Woodson Marathon’s owner, Lawrence Woodson, explained to WSET that these vehicle fluids “work better with the car if they are up to temperature.”

So what is the optimal time a car should be idling in the winter? A few seconds to a minute seem to be ideal.

Experts such as Popular Mechanics Magazine have reported that “a few seconds” is all a modern vehicle would need, because of the updated internal combustion engines of vehicles made after the 1980s. According to the magazine, prior to the 1980s, cars relied on carburetors as a crucial engine component. Without warming up properly, these carburetors would not have the “right mix of air and fuel in the engine – and the car might stall out.” This is where the original myth of leaving your car to idle in the winter began. However, during the 1980s, the auto industry moved away from carburetors and replaced them with electronic fuel injection. This technology uses internal sensors which adjust to temperature conditions and provide the right amount of fuel the engine needs. It also makes idling for five to ten minutes at a time useless.

Turns out, idling for long periods of time is not only useless but harmful to the vehicle. Stephen Ciatti, a mechanical engineer who specializes in combustion engines at the Argonne National Laboratory said to Business Insider that idling a car is “stripping oil from critical components that help [an] engine run, namely the cylinders and pistons.” When it’s cold outside, the mix of air and gasoline needed for the engine to run is different than during warm or temperate weather. As mentioned before, modern cars have internal sensors who increase the amount of gasoline in order to compensate for the cold. However, if the car is idling and not moving, the engine takes much longer to warm up properly. This means that a larger dose of gasoline is being used than necessary, and this excess can strip the oil off the engine walls if ran for an extended period of time. Business Insider explains that “the fastest way to warm your engine up is to use it, aka to drive!”

The Washington Post supports this claim by explaining that idling doesn’t do much for a vehicle, “but it does have several big (and avoidable) costs: Wasting fuel, and giving off greenhouse gas emissions and other types of pollution.” They site Natural Resources Canada’s research as proof. National Resources Canada is a Canadian energy and resources agency that ran a car idling experiment on fuel consumption. Their study found that “with a 5-minute warm-up total fuel consumption increased by 7 to 14 percent and with a 10-minute warm-up total fuel consumption increased by 12 to 19 percent.” This research showed that idling is much less fuel efficient than driving, because “whereas newer cars are constantly improving the miles they get per gallon driven, idling will always be stuck in place — using up gas, but getting no miles for it.” This makes idling extremely fuel inefficient and wasteful.

Idling also leads to an increase in harmful greenhouse gas emissions. A 2009 study in Energy Policy found that car idling is responsible for 1.6 % of all U.S. GHG emissions.

In the end, this myth of cars needing to idle for five to ten minutes in cold weather to warm up the engine has been busted. It may have been true decades ago, but today’s vehicles are better equipped to handle colder climates. In fact, they’re so well equipped that idling for five to ten minutes makes cars less efficient and may cause damage to their engines in the long run. It also strains drivers’ wallets and the environment.  As this winter season continues, a driver’s best bet is to keep idling to a minimum and get on the road to maximize fuel efficiency and vehicle operations.