Why Idling a Cold Engine Can Cause More Damage

In cold climates, it is practically a religion. On a freezing winter morning, you start your car, scrape the ice off the windows, and then let the engine run for five, ten, sometimes fifteen minutes before driving away. The belief is universal and rarely questioned. The engine needs time to warm up. The oil needs time to circulate. The metal needs time to expand gradually. Driving a cold engine must damage it, so idling in the driveway is an act of mechanical kindness. This belief is wrong. What actually damages a cold engine is not driving it gently. What damages a cold engine is letting it idle for extended periods.