A friend drove me in a Prius the other day. When we parked and he stopped the car there was a sound like a small pump. He said that the car has a "thermos" (well insulated container of some sort) into which oil is moved while engine is not working. That way the oil keeps most of the heat and the next time you start the car oil is already warm/hot (sent back into the engine of course). Is this true? Are there articles some place on this topic? What do you think? Would this reduce/eliminate cold starts damage? Comments.