Sometimes people will tell you that the best way to warm up your car is to let it sit idle until it does before gently driving away. This is a mistake. The truth of the matter is that letting your car sit idle for too long can harm your engine. It may negatively affect the life of your car. When I was a young lad learning to drive in Pennsylvania in the winter, I was always told that the best way to warm up a car on a cold morning was to start it, then drive away immediately but gently.
Older Cars Should Not Sit Idle
You are always encouraged to warm up a car by driving. This was to prevent you from decreasing the life of your engine. That is because your car actually warms up faster when it is in drive. When it idles for too long, the moisture in the exhaust condenses too slowly, and the oil doesn’t circulate through the engine enough. In worst case scenarios you are left with unburned gasoline that not only ends up coming out of the tailpipe to create smog, but it leaves your piston rings and oil at risk too. The older your car is, the more dangerous it is to let it sit idle. If you have a newer car, however, that is a different story.
Newer Cars Can (Sometimes) Sit Idle (for a Limited Time)
These days many cars are built with special remote starters. Automakers, aware of longer commutes now even encourage being able to sit in your car as if it was a mobile home or office. Climate control has gotten to the point where if you close your eyes you can envision you are on a tropical paradise while the cold winter morning surrounds you outside. A lot has changed.
Thanks to the engineering innovation of fuel injection systems, every fluid in your car is carefully metered and managed. You even have internal pollution-control systems. These help to keep precise measurements of fuel for your engine’s cylinders.
Be Cautious When Warming Up Your Car
Ok so the answer if you are truly harming your car by leaving it to idle on the driveway or parking lot for 20 minutes or so is: not as much as you used to. Of course you are opening yourself up to some wear and tear as opposed to actually driving but the problems are not as significant as they were on older cars.
Nowadays the biggest problem with leaving your car to idle is simply that you are now wasting precious gasoline. You are also emitting more greenhouse gasses than you would if you were just driving. So in the in the end the best way to warm up your car is still to drive it. You generate less pollution and wear & tear but also use less gas.