Oil pressure

[Signature620]

So you're saying changing the oil and filter improves the pressure? If the pressure readings are correct then something is contaminating the oil.

If fuel or coolant is getting into the oil it will thin it out and lower the pressure.
If carbon/soot is getting excessive in the oil it will clog the filter and lower the pressure.
If there is a significant oil leak inside the engine the pressure will drop more than normal as temperature increases (cracked gear housing, loose rocker shaft bolts, spun cam bushings, oil pump issues)