With 10w-30 oil, I am seeing hot pressure at idle somewhere under 10psi and at 2000 rpm around 30-35psi. Thinking these numbers indicative of loose bearing clearances, I switched to 15w-40 (after rebuilding the gerotor pump, which made no difference). With the heavier oil I picked up about 5 psi at both idle and 2000 rpm.

Would it be prudent to move up to 20w-50, stick with 15w-40, or revert to 10w-30? This is a stock-style street-driven engine.

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive