Every street and NHRA legal stocker 426 Hemi motors I've work on and raced always went faster and made more power with 10W30 than they did with 20W50Wt oil shruggy
Shorting up the bypass spring so the motors would have 70 Lbs. pressure with hot oil at 7000 RPM made more power than 80+ lbs. did also with the same oil temps. and RPM scope
10 lbs. per 1000 RPM with hot oil is a good scale to use up
I can remember when the NHRA Comp Eliminator races started using zero weight synthetic oils and changing it after every run to get .0015 ET gain shock scope

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)