03 2500hd ext cab allison trans. stock
while towing my travel trailer (4000lb) up i-5 over the mt. shasta grade
the oil pressure started to drop from 60 down to 30 up to 50 down to25
up to 60 i pulled of in shasta city and let eng. idle and cool down..idle
pressure was about 30 which is norma......shut off and checked for low oil
level o.k...........had lunch started up again and have never had this
happen again.........
whats up..............theengine performs as always......

Ron,


Mine also fluctuates on the big hills if I am in O/D. normally runs at or just over 60psi but when pulling hills in O/D, as I get my foot into it, the pressure will drop. Seems to drop as the boost goes up. I have no idea why and mine does it regularly. If I drop it to 4th and the RPM's come up so does the pressure. I posed this question some time back but never got a response. I am guessing it's just the gauge but who knows?

My 03 with a ZF 6 speed, the oil pressure gauge looks like my tachometer. At idle it's about 15 pounds, rev it up and it goes up to about 60. back off on the throttle and it goes back down. Is this something to worry about???????? Oh, and I have under 11,000 miles on my truck.


Jim

Your oil pressure will vary with the RPM of the engine since the oil pump is engine driven.


Low RPM = low Oil pressure about 20-30 for most at idle.


High RPM = higher oil pressure about 55-65 for most at 2000 rpm's.


All at tempature since a cold engine and oil will make higher pressure's.


I just had my oil pressure sending unit replaced at the dealer because it was fluctuating while driving. It was reading about half of normal pressure's then it would go back to normal. Come to a stop and it would drop to zero and the little bell would ring and the DIC would read Low oil pressure. Since the new one it's all better, even reads a little higher than before, about 65 at cruising speed.


Ron, have the dealer replace your sending unit if you can talk them into it or just replace it your self not that expensive or hard to do. Mine was intermintent too would happen for a few days then wouldn't for a few. Of course when I took it to the dealer it wouldn't do it, but I talked them into changing it anyway.


Jim, 15 lbs at idle sounds a little low compared to what others have. Are you using a good 15w40 motor oil?


Diesel Dragon

Yes, I'm using Delo 400 15/40. and I find it hard to go along with your explaination of the low a pressure at idle. All of the gas engines that I have owned, the oil pump is engine driven and I never had the oil pressure do that.


Jim

Jim the oil pressure always fluctuates from idle to cruising RPM up to a max point.


If none of your gasser's did that then the guages weren't very accurate. (espically ford's there oil guage never seems to move) Not that the one in our truck's is dead on.


Best bet is to hook up a mechanical guage to double check the factory one.


Like I said 15 lbs at idle seems a little low compared to others on the forum. If your truck has been that way since day one then maybe it's just the sending unit or maybe that's just the way your truck is. It's really not a problem as long as the pressure stay's consistent and dosen't start dropping down to 10 or 5 lbs.


My .02


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