While rummaging through my shed I found some quarts of Mobil 1 5w30, 10w30, and 10-40 probably from 2002. I wouldn't perform an oil change using these oils but should I keep one in the back of my Tahoe when it needs a quart between OCs? Is this when Mobil 1 was 100 percent synthetic? Then there was some formula change concerning the base stocks. All the bottles are tightly closed and not exposed to sun or heat and show no sediment at the bottom. Should I use it to top off? Thanks