oil pressure w/ bypass spring

[Gaz64]

Oil pressure at low speed is oil pump capacity minus the engine "leaks" (oil flow out of bearings etc)

Max pressure is relief valve spring.

I've seen engines with 10 psi at idle and 90 psi at 5000 rpm, and other engines with 30 psi at idle and 45 psi at 2000.

It all depends on the internal clearances of the engine AND the oil pump, then the relief spring pressure.