My truck seems to be losing oil pressure when the motor warms up. cold will build over 60 psi warms up and it drops to lower than 30 psi. Never use to do that. Any ideas dealership its the gauge. Also think I got a glow plug on the way out. As the glow light is on even when its 90 outside. Dealership cases that off to. Truck has 90000 and extend gmc warranty. Any advice would be great.

Any glow plug dtc's?
connect a mechanical oil pressure gauge and see if its with in specs. they can also compare gauge to i.p. gauge to see if its out.

My truck seems to be losing oil pressure when the motor warms up. cold will build over 60 psi warms up and it drops to lower than 30 psi. Never use to do that. Any ideas dealership its the gauge. Also think I got a glow plug on the way out. As the glow light is on even when its 90 outside. Dealership cases that off to. Truck has 90000 and extend gmc warranty. Any advice would be great.
The drop in oil pressure is normal. Could be that you need a new glow plug though.