Does engine oil go "bad" when stored outdoors in a car trunk in all seasons of the year? It was in the Seattle area where temperatures are not as extreme. Does it matter whether the plastic bottle in which it was sold and stored was opened or left sealed, in figuring out whether it has gone "bad"? I want to put it in an engine that has only 30,000 miles on it. Will "bad" or "old" oil harm a fairly new engine in any way?