Warming up a Car: Myth or Fact?

Whether from force of habit or misinformation, many drivers still think it’s necessary to let their cars idle and warm up before driving in the morning. While this may have been important 30 years ago, modern technological advancements have made warming up a car before driving a thing of the past.

The sophisticated fuel injection technology in modern cars has removed the need to “warm up” before driving. Photo: Coelho’s Body Repair (2013)

Prior to the 1980s, the fuel delivery systems in most cars were regulated by carburetors. With a carburetor, an engine needed to be warm in order to get the correct fuel mixture, which was why letting a car idle for several minute before driving was so important. By the end of the ’80s, however, a new kind of system was introduced: fuel injection. Not only did fuel injection produce lower emissions, it provided more efficient fuel distribution by adjusting and regulating the fuel mixture, which meant engine temperature was no longer a factor. By the 1990s, fuel injection had all but superseded carburetors.

With fuel injection, letting your car idle is not only unnecessary, it can actually contribute to engine problems such as a plugged catalytic converter (the device in the exhaust system that helps the engine run more cleanly by burning off hydrocarbons in the exhaust stream). Because leaving a car in idle is the slowest way to warm an engine, it can cause a catalytic converter to become overwhelmed, as it not only needs high temperatures to work properly, but is forced to work harder to combat the increased volume of unburned hydrocarbons produced by a cold engine. Over time, this can cause a catalytic converter to become “plugged,” and at the very least will detract from gas mileage and create dirtier exhaust.

Even if you’re still in the habit of warming up your car in the morning, remember that to maximize your gas mileage and keep your vehicle running optimally, you shouldn’t let your car idle for more than a minute before driving.