oil pressure

[redrider#1]

Anyone ever noticed the oil pressure gauge reading at idle while in drive? I just got my truck a month ago and not sure of the brand and wt. of oil the dealer used in it, but the oil pressure is around 20-25 psi at idle in drive with engine temp 205 degrees and outside temp 95-100 (this is just past the first white mark on the gauge--barely out of the red) Is this normal? I plan to change to Rotella 15w-40 at next oil change.

[JD Diesel]

Yep mines the same way. No problems thats the way they run. GM call for 15w40. JD

[redrider#1]

As always, thanks JD. I feel better now.

[Jim Brzozowski]

Did they change the gauges? Mine is graduated in 5 psi increments. If mine ever just came up to the first white mark I'd be plenty worried. You say you think its like 25 psi at the first mark? Sure thats alright, at idle.

[redrider#1]

About 20-25psi, as near as I can tell. The exact middle of my gauge is 60psi which is where it reads when engine is warm and running down the highway. I get much higher readings when engine is cold, of course, but it was the idle reading that made me worry.

[jbplock]

The oil pressure gauge on my 03 also ranges 0 to 120 PSI with 60 PSI in the middle. The gauge has 4 major tics with 3 minor tics in between... So each major tic is 30 psi and each minor tic is 7.5 psi (30/4). At hot idle it ranges between the third minor tic and first major tic or 22.5 to 30 psi. When istalling my oil bypass filter I also found the OE gauge compared well to a mechanical gauge. These gauges aren't instrument grade but they do yield a good relative mesurement when working properly.

smile.gif

[king kong]

I HAVE AN 05 WITH 79,000 MILES ON IT, AND i RUN 35 PSI RUNNING DOWN THE ROAD,AND 25 PSI AT AN IDLE. Do you think I should roll in bearings and a new oil pump. (GM says 42 min.)I use LE 15/40 change at 10,000 miles.

[mark45678]

King Kong... I run 5-40 syn oil in my 58K 2004.5 lly. I see around 20~22 psi at idle warm and 40~42 at a constant 70 MPH (2300 rpm area) HOT. its done this for 20000 miles , I dont see anything wrong with these ! if it blows you get a new motor if its under 100000 miles! ;)

[ballgyer]

I have a 05 with 9K miles. I too noticed that the oil pressure runs ~60 at start & 15-25 idle after warming up. I didn't see this this drop till after I got my first oil change (non-GM). I took it into the dealer thinking that the motor was about to fail. Turns out when the Dealer replaced the oil filter with one of theirs, the pressure went back up. Does any know of any differneces between the LLY oil filters & older motors?

[Driveshaft]

ON MY 01 LB7, I HAVE 75 IN AM COLD 60 TO 65 AFTER WARM UP AND 40 TO 45 IDLE. IN WINTER IT PEGS THE 80 GAUGE OUT WHEN COLD, THEN AFTER WARM UP IS BACK TO THE SAME #S AS IN SUMMER.

[Jim Brzozowski]

Driveshaft, I'm curious, How many miles do you have on the engine. You must have one of the tight ones.
My understanding is that at engine assembly the factory guys pick a set of rods that are coded, having been premeasured for diameter that fits the crank. Then they pick a crank that has been coded to fit within the specification and same with the bearings. The range of fits is a farily large range which allows them to use the parts even though they are not exactly what you would call racing tolerance ready. Because of the broad range of fits possible one can see how there would be a broad range of oil pressures observed during operation when fairly new.

What you describe for your oil pressure is where mine ran when new, but it has dropped some after some hard pulling and miles too. Now I wonder has anyone replaced bearings due to excessive clearance, or is the wear in the oil pump plus the heat on the relief spring of the relief valve in the oil pump causing the pressure to show lower than before? I think we all know thinout of the lubrication with higher temperatures is one factor, but what are some of the others?
Anyone replaced an oil pump due to wear and low pressure?

[Black95TD]

My new 005 LLY has about the same. 80 cold, 50-55 hot on the highway at 2000 rpm and 20 - 25 hot at idle. Still has factory oil since I'm at 1K now. I'm relieved that this sounds normal.

Another issue though - I have what sounds like piston slap at idle. Please see my new thread as I'd like to hear what others think about this.

17.5 mpg local driving - Thank Goodness!!

[Driveshaft]

SOTXPOLLOCK, I HAVE 54000 AND CHANGE ON TRUCK. THIS IS THE PSI THIS TRUCK HAS ALWAYS HAD. IT IS TIGHT, THOUGH. I ATTRIBUTE THIS TO THE FACT THAT I DON'T PULL AS OFTEN AS MOST OF YOU, JUST WHEN I DO I NEED A HD TRUCK. I HAVE FOUND THAT MY 2500HD WILL PULL JUST AS WELL AS A 3500. I PROBABLY PULL LOADS ONLY ABOUT 30% OF THE TIME. REST IS JUST BACK AND FORTH TO WORK OR TRIPS. MY WIFE'S CAR GETS MUCH BETTER MILEAGE, BUT WE ENJOY THE TRUCK MUCH BETTER. SORRY IT TOOK ME SO LONG TO REPLY, AFTER PUTTING IN 5 AND 6 DAYS A WEEK, 12 TO 13 HOURS A DAY AT THE COMPUTER, I AM NOT TOO CRAZY TO PLAY WITH ONE AT HOME.

[king kong]

I changed the oil pressure regulator ,and picked up 7 psi at 2,000 rpm I am now running about 42 psi. I feel better now . 81,000 miles.

[BlackMax 2001]

I also have a 2001 D/A. It almost mirrors what Driveshaft says his truck does. Use my truck almost the same way too. I just keep driving and smiling smile.gif

[David Proske]

My 03 has 43,000 miles. Hot idle is 35psi. At 70mph it shows a tad over 60psi.

[NUCLEARFROG]

I have noticed a considerable differance in oil pressures between my 03 LB7 with 48K milis and my 05 LLY with 4K miles. The LLY is about half the oil pressure through all rpm range compared to the LB7. I did the first oil change at 2500 miles. I have friends with both an 02 LB7 and a 04.5 LLY and their trucks have similar oil pressure to mine with the LLY being much lower. Is there a difference in the guage? sending unit? or oil pump? I sure would like to know why they are so different.

[Jim Brzozowski]

I heard somewhere that GM got them to lower the oil pressure to get rid of the infamous clacking sound that some of the first dmax engines made and so many questions asked about. I still run the 5W-40 year round, it idles at 35, and in 5th with TC locked it sort of keeps pace with the speedometer. 50 at 50,55 at 55, 60 at 60 and then levels off at 67 psig from there on up. Said it before, will say it again. You really only need 10 psig for every 1000 rpm to keep from hurting anything, If it ever goes less than that, I'd shut it off. I once had one of those SHO's with a Yamaha engine in it. The specs called for it to idle at 8 psi oil pressure. I thought they were crazy until I put over 200,000 miles on the engine and a lot of it at really high speeds. (I was younger and gas was cheaper back then.)Never had a minutes worth of trouble out of the engine. Didn't burn any oil when I gave it away, point being if they are right from the factory, oil pressure should never be an issue for any kind of engine, if you change the oil regular.