I always change my oil when it is hot. It folws better and that should cause it to get more oil out then when it is cold. A friend of mine changes his when it is cold because he says after it the car has been sitting for awhile all the "grit" in the oil is at the bottom of the pan. He says when you change it when it is hot after just running it all the "grit" is now all over the engine and not in the pan so it stays in the engine. Does he have a point? I know when you take a sample for UOA it says to take when the oil is hot.