Across the U.S., people who live in cold places often fire up their engines long before they start driving.
But this idea of idling your car in the winter is wrong. And so are the many Americans who believe it — one 2009 study found that, on average, Americans thought they should idle for more than five minutes before driving when temperatures were below 32 degrees.
Like many misconceptions, the idea behind winter car idling begins with a kernel of truth. Cars do get worse fuel economy when it’s really cold. And it does take longer for the engine to warm up and reach an optimal driving temperature in cold weather.
Older cars — which relied on carburetors as a crucial engine component — did need to warm up, according to auto experts. Without warming, the carburetor would not necessarily be able to get the right mix of air and fuel in the engine — and the car might stall. During the 1980s and early 1990s, however, the auto industry did away with carburetors in favor of electronic fuel injection, which uses sensors to get the right air-fuel mix. This makes the problem of warming the car before driving irrelevant.
Idling in winter thus has no benefit to your (presumably modern) car. Auto experts say you should warm the car no more than 30 seconds before driving. “The engine will warm up faster being driven,” the Environmental Protection Agency said.
So idling does nothing for your vehicle, but it does have several big (and avoidable) costs: Wasting fuel, and giving off greenhouse gas emissions and other types of pollution.
To show as much, Natural Resources Canada — the energy and resources agency of a cold country that also has serious idling problems — ran an idling experiment, freezing three cars to slightly below zero Fahrenheit and driving each one the same distance. Sometimes the cars were idled five minutes before driving, sometimes 10 minutes. The result was that the more idling time, the more wasted fuel.
But it’s not just fuel waste, it’s the accompanying emissions. What does it look like when you have a whole population of people — or at least the northern belt of a country like the U.S. — idling their cars in winter?
A 2009 study in Energy Policy tried to calculate the consequences. The researchers found that, overall, all types of vehicle idling — idling in winter, idling while waiting for someone or something, and idling in traffic — contribute a staggering 1.6 percent of all U.S. greenhouse gas emissions. That number is “almost double the total emissions for the iron and steel manufacturing industry,” the paper noted.
That is not to say that all idling should be stopped immediately. Some idling — particularly in traffic — may be unavoidable. But the other two categories of idling — in winter and while waiting — make a lot less sense. And the study found that they account for nearly half of all U.S. greenhouse gas emissions attributable to idling.
