So I've searched the forum and found some things like this but not exactly. Like others have had happen, my oil pressure gauge fluctuates. It only happens after the engine is warm. While driving, the pressure reads 40-50 psi. Put at idle, either in park or drive, the pressure drops to 20 or lower. A few times its dropped so low that my check gauge light comes on in the dash. Is this a problem with the sending unit? Or would replacing the oil pump solve this issue. I already have to drop the pan to replace a leaking pan gasket, so I'll already be into the engine. Any advice would be great. Thanks guys.

 

I would suggest that's it's the oil sending unit verses the oil pump. Have the sensor checked.

When was the last time anybody heard of an oil pump failing?

 

I would say it is not the sender. You may have a pump issue, but more then likely you just have a tired engine. When the miles get up there and the tolerances increase ever so slightly your situation becomes very common. My 98 5.7 was starting at about 50 PSI in the morning and as it warmed up would drop to around 20 at idle as well. The truck is new to me and I just changed the oil for the first time and it seems better, but still drops from around 60 to 30. Try an oil change and even some additive like Lucas to see if that helps keep the level up at idle. It wouldn't be a bad idea to give the oil pump a visual inspection when you have the pan down or if you have the funds to go ahead and replace it while your there. Also make sure the oil pan doesn't have any sludge or anything that could be partially clogging the pick-up screen. Good luck!

 

if pan comes off always change pump but in you case alot of those have problems with the sending unit they seap and cause low readings at idle also check for worn grounds or a plugged oil cooler