My cars oil pressure is at 50 when idling cold. When it gets warm it idles at 18psi, revs up to about 30psi. This is on a mechanical oil gauge. Running straight 30 weight.

It's not perfect, but it's not horrible. Probably some inaccuracies in the gauge and some bearing clearances off.

When the motor was built what were the main clearances? If tight, say .002, thinner oil will be better, if sloppy, say .0050, you want thicker oil.