Originally Posted by ThermionicScott

When it comes right down to it, internal combustion engines are "happiest" when run continuously and never turned off. The vast majority of wear comes when starting a cold engine. But, especially in cold weather, it takes a while for the engine to reach the optimal temperature and boil off the water vapor and fuel dilution, so all of these well-intentioned running cycles can do more harm than good. That's why it's best to limit them, and make them count when you do them (highway runs are best.)