In cold weather, if you think it’s a good idea to warm up your vehicle’s engine by letting it idle several minutes before driving, you should think again.
Multiple news outlets, from The Washington Post to Road & Track to Popular Mechanics to Business Insider, all cite experts who call the concept a myth. Beyond that, these experts emphasize that letting your vehicle idle for lengthy stretches actually does damage to its engine.
Road & Track points to a persuasive video, “Should You Warm Up Your Car?”, produced by Jason Fenske of the Engineering Explained YouTube channel. During the video, which has received more than 1.7 million views, Fenske explains modern, fuel-injection engines (unlike carbureted engines of the past) warm up faster from a cold start when you put them in motion and actually drive them.
“Idling the engine does not put much heat into it,” Fenske says, “so the car remains cold for a long duration.”
Why is this? Business Insider turned to Stephen Ciatti for an answer. Ciatti is a former drag racer who holds a PhD in mechanical engineering and oversees all of combustion engine study conducted at Argonne National Laboratory in Illinois.
Ciatti points out that idling your car in the cold produces two negative outcomes: It wastes fuel, and it dilutes the oil that lubricates your engine’s cylinders and pistons, some of your engine’s most vital components.
All of the cited publications explain that in normal weather, engines use a mix of vaporized gasoline and air to operate. Once that mixture fills a cylinder, a piston compresses it and combustion occurs. This action powers an engine.
In cold conditions, however, gasoline does not evaporate easily. Engines respond by adding more gasoline to the air-vapor mixture, meaning they run “rich.”
Because gasoline is an effective solvent, though, it can strip away protective oil from cylinder walls (see the first 90 seconds of Fenske’s video) and accelerate wear patterns. If you let your engine idle in cold weather, you leave its cylinders vulnerable to damage due to diminished lubrication. This can shorten your engine’s life.
What’s the right approach to your vehicle on a chilly morning? Fenske recommends starting your engine and waiting just 15 to 30 seconds, simply to ensure oil is flowing. “But you don’t need to wait for the engine to be warm,” he explains. “It will heat up faster by driving the car lightly. By heating it up faster, the oil gets to operating temperature more quickly, and this is what you want to prevent wear.”
Other experts opinions cited in this collection of articles suggest that sufficient warmup time is 30 to 60 seconds—about the length of time needed to brush snow off a car’s windows. Then start driving—but just lightly, as Fenske describes it.
Driving “lightly” means applying a light foot on the accelerator. Don’t gun the engine or floor the pedal. The Business Insider article her estimates an engine needs five to 15 minutes of drive time to warm up and reach 40 degrees Fahrenheit, when an engine’s fuel-air mixture achieves a normal ratio (and no longer runs “rich”).
What if you drive an electric vehicle? Cold weather drains an EV’s batteries faster than warm weather. In a separate article, Business Insider quotes another expert from the Argonne National Laboratory who points out a common mistake EV drivers make: warming the vehicle’s cabin before driving.
The recommendation: Plug in the vehicle before you drive it and use the external power source to heat the cabin. Usually a driver can activate this process remotely (and in a warm, indoor place), using a smartphone app. And, once on the road, use seat warmers for warmth rather than the cabin heater, which typically drains battery power at a faster rate.
To learn addition tips for optimizing an EV’s driving range in winter months, refer to a list of tips from Green Car Reports.
Meanwhile, for drivers of conventional vehicles with fuel-injected engines, reject the myth. Don’t bother warming up a vehicle’s engine in cold weather. You’ll save fuel, reduce engine wear, and avoid releasing unnecessary pollutants into the air.