For the millionth time your
oil pump is a positive displacement pump. Regardless of
oil pressure flow is the same EXCEPT when you exceed 60 psig. 60 psig is when most
oil pump internal relief valve relieve. This means you get LESS flow with heavier oil because the oil pump relief valve open with less flow do to higher flow resistance and dumps to the oil pan instead of going to the engine. So with lighter oil you get more flow when close to 60 psig, you get better cooling and you get lubrication. No reason to run anything heavier than 10W30. You are much better off running
zinc additive then heavier oil although with a roller engine you dont need anything.