Mack cxn613, oil pressure drops when warmed up.

What's the psi running hot and cold? Both of ours run 60 psi at highway speed and 30 idle hot

 

I'll go look at the book in a sec but I believe hot idle at 650 is supposed to be 15-30 and 45-60 on the road I think. I wouldn't run that until you fig out the issue. Not that big of a deal to drop the pan and check to see if the pump is within spec.

10psi is really low for hot idle. If my oil temp is up around 190 it goes down to 25 but shoots right back to 30 after a few min to cool down idling. How many miles on her. Ours has 100k on inframe and the other 500k

 

I have 3 of those getting fuel in the oil.
#1 had pipe plug in the front block fuel galley leaking. Looked like the factory dry loctite had desolved.
The other plug next to it was also loose.
#2 and 3 had a leaking fuel supply pump.
You cannot see anything about those from the bottom other the fuel leak from the front. Is it over full of oil?
One of the three was out of state like that. We had the oil and filters changed. Pressure came back up and drove it home.
If you thank and or test it has fuel in oil remove the fuel supply pump first. Hook the lines and all back up and build pressure with the hand pump. It is common for the shaft seal to leak and you can see that.

 

Mechanical pressure gauge ? Dash gauges lie all the time