I apologize if this is a dumb question, but here goes.... My questions is...does oil have a shelf life where after a certain point it doesn't provide as good as protection as it would have when it was first produced? If so, what would be the normal "shelf life" for automotive based oils? What I'm getting at is I'm like alot of people, if I find a good deal on oil products, I like to stock pile it for later use. Of course later use might be days, months, or several years without being poured into your vehicle. My opinion would be yes,....but I have no clue as to how to calculate this. Of course, my opinion is based on seeing expiration dates and best used by dates on other household products, medicines, etc... Thanks!