1998 pontiac bonneville oil pressure low

I have a 98 pontiac bonneville that runs at about 40psi at start up but once warmed up will drop to the red around 5-10 psi. I have had the pressure checked manually and it reads an average of 32-38 psi so it cannot be internal. I have also replaced the sending unit and it still does it. I have noticed a couple of times the instrument cluster will all of a sudden go dim or get really bright all of a sudden also. Does anyone have any ideas what this could be knowing it is not the sending unit and is not internal. Thanks

I have a feeling that the instrument cluster has some loose connections or a bad circuit board. If the guage is incorrect but the pressure is good then the problem has to be with the guage readout. You can either replace the instrument cluster or purchase an aftermaket guage for oil only and mount it somewhere on the dash. It is usually easier to replace the cluster than try to repair it unless you can find out what part of the circuit board is bad and have it repaired.

I have the exact same problem and have performes the same test myself and at idle I have 35-40 psi. and anywhere over 1200 rpm I am at 60+ psi. The only thing I haven't tried is a factory Delco sending unit. I am curious of what you found on yours. Mine is a '98 SSE.