Oil

Check the oil level. Remove the oil pressure sender and clean the screen and if that does not fix the problem you can either replace the sender or use a mechanical gauge to check the accuracy. If these things fail to fix the problem your engine/oil pump are probably worn out.

I agree with f o r. The oil pump speeds up and down with rpms, just my opinion. You could use analog gage in place of sending unit to double check oil pressure. In the old days, they use to say 10 psi for every thousand rpms, I'm not sure that's valid, anymore. Generic oil pressure spec, 20--30 psi at idle, 40--60 psi at cruising speed. You need proper specs for your vehicle. I don't have that in front of me. Everybody have a good day.