Idling = Zero Miles per gallon

There's a very common myth about winter driving that leads to a tremendous amount of waste and air pollution. Most people believe that when it's cold outside, that you still need to idle a car for an extended period of time before driving off to avoid causing mechanical damage. That might have been true once upon a time (in the era of carburetors), but modern engines and modern oil only need a relatively short warm up period; after that, the best way to warm up a vehicle is to drive it (granted, if you're going to immediately jump on a highway and drive at high speeds, you might want to warm it up a bit more, but for regular low-speed driving, there's no need).

Don't believe me? Here's the U.S. Department of Energy:

Avoid idling. Think about it -- idling gets you 0 miles per gallon. The best way to warm up a vehicle is to drive it. No more than 30 seconds of idling on winter days is needed. Anything more simply wastes fuel and increases emissions.

Not good enough for you. You think the DOE doesn't know about real winter weather?



Flickr/CC BY 2.0

Here's Natural Resources Canada:

Contrary to popular belief, excessive idling is not an effective way to warm up your vehicle, even in cold weather. The best way to warm it up is to drive it. In fact, with today's computer-controlled engines, even on cold winter days, usually no more than two to three minutes of idling is enough warm-up time needed for the average vehicle before starting to drive – but make sure that windows are free from snow and properly defrosted before driving away!

So maybe a few minutes when things get really cold... But the fastest way to warm up a car is to drive it, so you're just making the process longer and more wasteful by idling more than is truly necessary.

Obviously, I'm only speaking about what is necessary for the engine to be fine. This doesn't mean that you should jump in a car that is covered in a foot of snow and drive off; you still need to de-ice the windows, remove any snow that blocks visibility, etc. But this should be done with good old muscle-power, not by idling a car so long that it warms up enough to melt the snow in the windows!

The Argonne National Laboratory has also looked into the issue and recommends against the need for long idling before driving. They've created this nice little graph that shows that - as with driving in general - larger engines waste more gas over time when idling:

Argonne Lab/Screen capture

This myth about idling engines in cold weather is so pervasive that the consequences are quite harmful. A 2009 study estimated the impacts:

Those who held inaccurate beliefs idled, on average, over 1 min longer than the remainder of the sample. These data suggest that idling accounts for over 93 MMt of CO2 and 10.6 billion gallons (40.1 billion liters) of gasoline a year, equaling 1.6% of all US emissions. Much of this idling is unnecessary and economically disadvantageous to drivers.

The environment and your wallet will thank you!

So we still encourage you to be a badass and take up winter biking, but if you have to drive, at least don't waste gasoline based on a myth.