Nissan Repair: 1990 300zx oil pressure, oil pressure gauge, oil pressure switch

Question
I have a 1990 300zx that i purchased about a week ago.  My first Z :)  When i start it cold the oil pressure is around 30-35 psi at 2500 rpms.  When i come to a stop, it drops between 5-15 psi.  As soon as i accelerate, it goes back to around 30-35 psi.  The pressure doesnt fluxuate at all while driving.  What is the normal oil pressure while driving and stopped?  Should the pressure fluxuate at all?

Answer
Greg,

The oil pressure gauge is sensitive and provides accurate readings at idle and at speed.  COmpared to most cars out there where the pressure pops up and stays there the Nissan gives you accurate readings.  You need about 10 pounds at idle.  Basic rule here is 10 pounds for each 1000 RPMs.  If you are really showing 5 pounds at times would lead me to first change the oil pressure switch on the engine to see if the old one was lazy or getting plugged up.  Also, make sure the car has a proper idle.  If you hear rod bearing noise, at idle, would lead one to think the oil pump is wearing or the rod and main bearings need to be replaced.  Basically, that is the order I do things in when dealing with indications you describe.