When I rebuild an engine I use "Super Lube Teflon Grease" on the drive gears, it never dries out or hardens and engines I've rebuilt 5 years ago are still running fine. I use it on the wheel trucks as well, but VERY sparingly, just a very small amount works and it does not attact dirt. You can find a 3 oz tube for about $5 and it will last a long time. Radio shack used to sell something similar, but now all they seem to sell are phones.