Outer Limits 4x4 Board

have a 4.2 diesel ford maverick
using penrite hpr 20w 60 oil
i have changed oil filters from z115 to donaldson filters made no differance oil light still stays on for at least 6 sec
oil pressure at idle when cold 60 psi
when hot at 100 klph in 5 gear still 60 psi
my after market electric sparco oil pressure gauge the needle some times jumps between 50 - 60 psi
could some one please explain to me or tell me how to cure oil pressure light staying on for so long and why my aftermarket gauge needle jumps around thanks

sounds like the original sendr unit has died and you are getting volage fluctuations on your gauge set up

20/60 oil is very thick oil.

what does nissan suggest for your motor ? 15/45 ?