I posted a similar topic in the 12V section, but it's not getting many hits. Short story is that after 80 miles of interstate driving, running Rotella Synthetic 5W-40, I got a low-oil-pressure warning light at idle. The "inaccurate" dash gauge read just under "40." Only happens when fully warmed up, 45 minuites of driving or more.

Hooked a real gauge onto the 1/8" NPT hydraulic port on top of the oil filter - and with the engine hot (but the light not on) it read a solid 18 psi. High idle is about 65 psi, 1800 rpm about 45 psi. "Cold start" (85* F) at idle it was at 50 psi. Does anyone know the Cummins low-acceptable pressure at idle with the engine warm?

I'll probably switch back to Rotella 15W-40 mineral oil - it's always worked fine. Thanks for any help...

 

Sounds right. On my engine after the oil was nice and warm it was around 20psi (rotella 15w-40). Cruising down the highway around 1700-1800rpm it was around 45-50psi. WOT it was ~60. On a cold morning though it would peg my 100psi gauge at idle.

 

Something tells me the sending unit is shot, mine is at 40lbs at idle, and 60-65 under load.

 

How could it be the sending unit when with the mechanical gauge, I'm bypassing it completely?

 

The manual for my '06 claims these points acceptable: >10psi at idle and >30psi @ 2500rpm.

HTH

Tony

 

Same points for a '96 as well.

 

mine idles at 20 psi with amsoil.

 

So do the stock sending units read high at idle, and maybe low at WOT? Mine went out a while back,and the new one reads lower than the old one at all times. I want to stick a gauge on the port and see what I really have.

Eric

 

I have about 15 at idle and 50 at 1800.

 

I had not heard that 5w40 oil was approved for use in a 96 engine so that may be part of your problem with low oil pressure on a high mileage engine. My self I used Rotella 5w40 and after 3800 miles I got rid of it and went with Amsoil 5w30 and my truck now runs quiter at all speeds then it did with Rotella 5w40 in it.