Custom Baggers recommends and uses Torco US Made top quality oils, as many drag racers have found they do not break down like conventional oils if you use synthetic- or lose their viscosity under extreme heat with no black sludge problems- ending your engine life! Having had a cheaper brand in plus degrees break down blowing the big ends on my bike-and getting recovered from Austria plus huge expense of motor rebuild of a SPUTHE motor - NEVER again will I use anything else: Mike