Dear Car Talk:
I know newer cars don’t need a warm-up in the winter months.
But does it really hurt the vehicle? When it’s 0 degrees out, I want to enter a warm toasty car. So a good 10 minutes with the engine running helps me. Does it hurt my car?
— Brian
No. In the old days, when cars had carburetors and chokes, excessive “warming up” was bad for the car.
Here’s why: Carburetors were such imprecise devices, that when the choke was set on cold mornings to prevent the car from stalling, gasoline would pour into the cylinder as if it was being poured out of a 55-gallon drum.
And you’d get so much gasoline in the cylinders that not all of it could be combusted. And until you “reset the choke” by driving away or jabbing the gas pedal, the gas would continue to pour in, and some of it would seep past the rings and mix with the oil. What’s the problem with that? It would dilute your oil and degrade your engine’s lubrication.
And if the car had a catalytic converter in those days, you’d also shorten its life by sending tons of unburned gasoline through it to be catalyzed — not to mention the rare, but real risk of setting the car on fire by overheating the converter.
But nowadays, fuel is so precisely metered by computerized fuel injection that the cylinders get only — and exactly — what they need. There are no more barbaric, mechanical chokes that pour in fuel while the engine races at 3,000 rpm.
On cold days, modern engine management systems will raise the idle speed a little bit, to say, 1,100 or 1,400 rpm, and only for the first 15 or 20 seconds of operation, and then drop it back to 700 or 800 rpm. So, you’re simply not pouring in fuel that goes unburned and there’s really no danger of diluting the oil or abusing your catalytic converter.
Any downsides, therefore, are not to the car. You’re wasting fuel and spending that money, you’re creating more pollution, and if you live in tight quarters, you might be annoying your neighbors.
But are you harming the car? No. So on bitterly cold days, you can warm up to your heart’s — and butt’s — content, Brian.
