We ran Valvoline 10w30 racing oil for years. Switched to Amsoil and saw a big difference in the appearance of the parts when we did our winter freshen and in the trash coming out of the filter, which we looked at after every weekend-even with the oil restricted to the cam and the top end. Also went from changing oil every dozen runs to every 50 or so, based on the appearance and smell of the oil.

With the Amsoil, we tried different weights from 10w30 to 0w20. The oil pressure with the water thin stuff got to be a little concerning, so we settled on 10w30, rather than tighten up the clearances. Clearances and internal leaks have to be adjusted and/or fixed depending on which weight oil you are using.