Hello all,

I have a 2005 GMC 2500HD, 6.6L turbo Duramax diesel. I have noticed lately that at idle my truck is around 15-20 psi. Also if I am going say 55 mph and let of the gas the oil pressure drops to 15-20 psi. Is this normal? I went to the dealer already and they replaced the sensor from what I know of. Also seems that a new oil change doesn't change the conditions either. Any help would be much appreciated, Thanks.

This is from a GM PI.

Condition/Concern:
The Engine Oil Pressure reading is low or near the red zone when coming to a idle.

Recommendation/Instructions:
Complete the current SI diagnostics for any trouble codes or symptoms found. If the customer concern is only the oil pressure gauge reading low, and they are comparing the reading to a older model diesel engine, compare the gauge reading to another 2004-2005 LLY diesel engine equipped vehicle. It is normal to see the oil pressure gauge near the red zone after running the engine and coming back to idle.

If the low oil pressure warning message/chime is on, follow the current SI diagnostics for Oil Pressure Diagnosis and Testing and/or the Engine Oil Pressure Gage Inaccurate or Inoperative. Complete necessary repairs using SI information.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

Sounds normal to me. I am running synthetic and these are typical of what I see.

this is how mine is also. Thats how its suppossed to be as far as I know.
I run 5W-30 synthetic.

Alright guys thanks for the responses, I was a little worried for a while. :)

It has a lot to do with what oil you are using. Saying "synthetic" doesnt really cut it as far as oil pressure. I ran Rotella synthetic for about 4000 miles and the oil pressure would drop down to around 15psi at idle. I dont like seeing any gauge that close to the lower limit, so I put Mobil Delvac 1 in and now at idle I stay right around 25psi. Mobil 1 doesnt turn jet black the minute you start your engine after an oil change either. Sounds to me like your running junk oil. Mobil 1 may be more expensive, but its good stuff, you get what you pay for!

Well it could be, but I've had my oil changed by the dealer so not sure what they have been using. Ill see what Mobil 1 will do, thanks for the help!

I see the same pressure, around 20 psi, using rotella synthetic 5w40. I have used conventional rotella 15w40 but I don't recall what the pressure was at idle.

With Rotella or Delo 15W40 mine idles hot, one notch above the red which I think is 15-20psi. I think this is normal.

At 2000 RPM warm engine it's a shade under 60psi. If I pull a trailer up a hill in the hot summer (So Cal coming out of El Centro towards San Diego for example) with the cruise on, it will stay at 2K RPM but the oil pressure drops down to +/- 45 and returns to almost 60 on the down hills. I've never seen more than 210 on the temp gauge but my predator said 234 ECT on that hill.

I don't know what the normal engine oil temp in a Duramax is but I'd say it gets pretty frickin' HOT. Makes me want an oil cooler and I'd be afraid to put 5W30 in it at least not around these parts.

In My Lly I Lost A Motor At 27k I Had Been Using Delo,and Had Complaioned About The Low Oil Pressure But Was Blown Off,now In My Dealer Replaced New Motor I Run The Mobil Delvac 1300, Good Oil Pressure At Idle ,so Far So Good.

I was told at the stealers that the Duromax works fine with as little as 8 lbs of oil pressure.;)