How long do you guys let your car warm up?
I usually warm it up for few minutes. When really cold, at least 5 minutes. But I've been told otherwise. Some say it will harm the engine if you let it idle to warm up for few minutes before you drive it... I always thought it does more harm to drive the car when still cold as the oil is too thick to adequately protect vital parts of the engine. Why would you want to put stress under these condition? I have always followed the cardinal rule to warm up your car before driving and always change oil within 4k miles. I have kept most of my cars till ~150k miles. And all my cars, even American made lasted without engine problems.
See following arguments why you shouldn't warm up your car.
1. for one thing it "fouls" the plugs.
2. Part of the problem has to do with the fuel system.... When the car is cold the ECU is running the car in "open-loop" mode until the O2 sensors warm up. Until this happens, the car is running from a hard-coded fuel map, which runs the car very rich until the O2 sensors heat up to a sufficient temperature, at which point the ECU switches over to "closed-loop" mode.
When the car is at idle, the oil pressure is low. Low oil pressure, combined with a lot of gas going into the cylinders is like "washing" the cylinder walls down with gas, greatly increasing friction and wear. Under load, your oil pressure will be higher, which will prevent this from happening, even though the oil is cold and thicker. Besides, the engine will warm up faster under load than it will idling.
