I recently ran across a nearly-full and sealed box of Multigrade in my garage -- must be at least 4 years old, probably around 7. Top half of the box: fog. Bottom half: okay-ish. Should have been in a dark place the whole time, could it have been fogged by Hawaiian weather, or... ? Hmmm. Either way my confidence is low, I wrote "Emergencies Only" on the box and put it back on the bottom shelf