2002 Dakota SLT
4.7L
150k+ miles, top end rebuilt after overheating last year.

Oil pressure drops on gauge when idling after truck warms up, then goes back to normal level after RPMs are raised.

It started right after a oil change and didn't always happen. Now a few months later it constantly occurs.

Any ideas?

 

Yeah, the oil pumps are mechanical so the "problem" you mentioned it typical. As long as it stays between the bottom and top hash marks you are fine. You could always get a line pressure tester thingamajig and self check it to verify the pressure.

 

Could be your sending unit going bad..

 

I was thinking sending unit too, I changed the oil today as well. So far has been good