My advice, run nothing but Tamiya in the gearbox. With a fresh set of gears and a new 20t it should run for a decent amount of time without a hassle. For the price, i usually have 2-3 brand new 20t tamiya pinions in my box, and swap them out before they destroy the gearset. As for lube, i used to use silicon spray, but now i dont even bother. I use nothing in the gearbox, the gearsets cost $7-8 and the pinions about the same. Any decent lube will make your gearsets last longer, but we run silvercans, and thick lube will create drag.