I understand the reason for multiweight oils. My question is this. Using a 5w30 oil as the example. Is it a 30 weight, with additives to make it flow like a 5weight when cold, or is it a 5 weight, with additives to make it protect like a 30 weight when hot ? Or , is it a say 15 weight, that has additives that take it in both directions ? I realize the answer may not be as simple as I have presented it here, but just for the layman, I am curious.