Oil Pressure@ cold start

[Frank Orozco]

Hey guys,
            I was hoping someone on the list would know whats going on here.
A search of the archives turned up nothing.

My oil pressure @ cold start used to be dead nuts at 61 psi, now it wont go
past 48.  It happened after changing my oil, but I didnt try a new weight,
I am still using the same Mobil 1 synthetic 15w-50 I have always used.  The
only thing that was different was I had to use a Fram filter, because I was
out of Nissan ones.  I figured this might be my problem, so I switched to a
Mobil 1 oil filter ($12!) and am still have the same problem.  What could
this be? Is my oil pump giving up the ghost?

Oil Pressure when warm is completely normal.  15-20 psi at idle, hovers
around 51 psi during freeway driving, and 60 psi on wide open throttle runs.
Thanks guys.

Frank Orozco
1996 200sx SE-R
F-MAX Stage 2
340 whp/380 ft lbs.