you need no additives, maybe some stabil in the tank if you don't drive it a lot, but I even have my doubts about that. All additives do is remove money from your wallet. As was said above, the best thing to do is drive it regularly, long enough to get it up to temp for 20 minutes or so. What exactly would you be lubricating in the upper engine, the top of the piston? These engines are so inefficient, they don't produce enough combustion heat to really hurt any thing in regards to the hardened/lack of hardened seats.
