My builder specifically built my engine for 20/50 high
zinc dino
oil.
Roush builds motors specifically for 10/30 with tight tolenances. So putting 20/50 in there is not a good idea.
Engine builders have their own recipes for tolerances etc...
There is no "one size fits all" scenario.
Just for kicks I tried 10/30. Lost 10lbs of pressure. Switched back to 20/50 and was right back to 25 idle about 60lbs driving. Right where it should be.
Have about 15k on the engine. Never a problem, and the
oil flows on the rockers perfectly.