Obviously depends on RPMs. Normally 15-20psi at idle. Could be as high as 30-40psi when the engine is under high RPMs.
Plugged PCV valve or hose
Oil pressure ( Minimum ) 1000 RPMs 6 LBS 2000 RPMs 18 LBS 4000 RPMs 24 LBS It must have at least that much oil pressure at these different RPMs to LUBE the engine. If it has 80 LBS are more then the oil pump check valve is not working correctly
put on a new PCV valve.
White smoke is usually do to water in your system. That happens when you blow a head gasket, or have a cracked head. If your oil level is high check your oil for water, if so that's were your coolant is going. All in all you have a blown head gasket.
Oil pressure ( minimum amount ) is 6 LBS. at 1000 RPMs. 18 LBS. at 2000 RPMs. 24 LBS. at 4000 RPMs. more pressure is fine too.
Probably a worn out engine.
Typically its either worn or broken Piston compression rings.
This can happen on a high compression engine (especially diesel) when the oil is not changed often enough. The fuel blow-by from the rings causes fuel to mix with the oil and "coke up" , creating oil that looks almost like asphalt.
your problem is your oil pump.it has a blow by ball and spring to release excess pressure and it is stuck closed. replace oil pump !
Excess fuel causes black smoke.
Advertised engine oil pressure is: 1000 RPMs----6 LBS or more 2000 RPMs-----18 LBS. are higher