On cold winter mornings, some folks will fire up their cars and leave them running for 10, 20, maybe even 30 minutes, thinking they’re reducing wear and tear by letting their cars warm up gently. But Jason from Engineering Explained is here to explain why that’s a bad idea for your car.
(This post was originally published on August 3, 2016 and has been republished because it’s getting damn cold outside for much of the country. – Ed.)
The conventional wisdom that you should idle your car up to operating temperature comes from the days of carburetors, which needed several minutes of idling to get to an operating temperature where they’d run smoothly. With fuel-injected engines, the ECU can adjust itself to idle perfectly even in sub-zero weather. And as Jason explains, idling an engine doesn’t really build up much heat at all, compared to driving it.
Jason goes through the details of what happens in a cold engine, and points out the hidden damage of letting your car idle for a long time on a cold day: Engine oil dilution. It turns out, while you might have thought that letting your car slowly warm up was reducing wear and tear, all that idling time leads to raw gasoline seeping into the oil, breaking down the oil’s lubrication properties and increasing the wear.
So what should you do? Start it up, make sure all your windows are clear of ice/snow/fog, and just drive the thing! The engine will warm up faster, and therefore you’ll get nice warm heat coming out of the vents sooner, which is what you want anyway.
Watch for yourself and let a real engineer explain why you should stop warming up your car.