Modern cars aren’t hurt by idling to warm up
Best approach still start it, drive gently
DEAR CAR TALK: When I was learning to drive in the winter, I was always told that the best way to warm up a car was to start it, then drive away immediately but gently. It was common wisdom that to let it idle was to decrease the life of the engine, since nothing warmed up quickly enough: The moisture in the exhaust would condense more and rust the muffler; the oil would be sluggish, and thus the engine lubrication incomplete. Now we have cars with remote starters, and we can start the car as we sip our morning coffee, so the car is tropical when we finally start out. What has changed? Are cars really designed for that abuse? Or is it a case of our laziness winning out over good car sense? — Richard
Historically, laziness always prevails, Richard. But these days, it’s not doing much harm to the car.
In the old days, when you started a cold car, the carburetor would pour gasoline into the cylinders almost indiscriminately. Then unburned gasoline not only would come out the tailpipe and cause smog, but it also would find its way past the piston rings and mix with your oil. That meant your engine was being lubricated with gasoline and oil, instead of just oil. So the engine would suffer.
But these days, all cars are fuel-injected, so the fuel is very carefully metered. Sophisticated pollutioncontrol systems ensure that only the precise amount of fuel that’s needed goes into the cylinders.
So, do you harm your car by warming it up in the driveway for 20 minutes nowadays? Not really. Obviously, you’re putting a small amount of wear and tear on the engine by running it when it would otherwise be doing nothing. But gasoline no longer dilutes the oil. And the moisture in the exhaust system is an issue only if you run the car for a brief period and then shut it off. If you drive away, that moisture will eventually evaporate.
The biggest issue, really, is that you’re wasting fuel and creating more pollution than you would have if the car were off.
But you’re still right, Richard, that the best way to warm up your car is to start it up, and if it starts, gently drive away.