This is something I've always wondered. Does moisture get into the oil right after you have shut the engine down and the oil is cooling, or does it get created right after you start the engine from a cold start? One of the reasons I am curious, is because I'm trying to figure out if I have properly stored my cars in the past for the winter. I would usually change the oil right before storage, but I would drive the car and fully warm it up before putting it away. Should I have simply changed the oil and poured in the new stuff and not started the engine?