I've used Valvoline 5W20Wt oil in my street and strip motors for dyno testing for years due to no HP gain or loss on oil temps. from 80F to 220 F with loose clearances like I posted already. As far as synthetic oils I don't like them due to many bad results from switching to them during dyno tests years ago Maybe I will try again, maybe not
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)