1950 mercury flat head

what oil does everyone use in there flat heads---i know i have to use the zinc additive----i am using Rottela 15-30--using alot of oil---motor just rebuilt---ty

 

Seems some guys are just using good old 30wt....bumping up....also check the "Banger Thread" right here on the HAMB for suggestions........

 

Shouldn't be using "a lot of oil"Rotella is fine,or straight 30.