I don't have the receipt and don't want the hassle of trying to prove I bought it there.That's a great offer! However, have you ever thought about taking it back to the store and trading it in for non-synthetic? They might do it even without a receipt as long as you only want to trade it back in. Not that I don't want to drive there and pick it up!
OK, well if he doesn't pick it up, please let me know.