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Discussion Starter #1
I had seen several posts about oil pressure. Most folks said the presure changed due to the year and type of oil. I had an 02 and have had an 03 for about a year. Both trucks started out with the same Rottella oil and then were switched to C5, Delvac 1, around the 24-26k range. The pressure was exactly the same between the two. The switch to C5 droped the psi about 10 lbs, that's it. Well, I just changed my oil again and now my pressure is down? I checked everything and there is but one difference----> For the "first" time I am using the "AC Delco" blue filter instead of my usual "Iszzu" black filter. I wonder if GM made this filter to cut down on the "Tick" that most of us have before the motor breaks-in.


If I can.......No, I will find an Iszzu black filter this week.


--- I'll get back to this post as soon as I switch back to Black.






Burner--------->
 

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Napa gold built by Wix and no pressure issues.


Delo 15w-40 400 is the only oil I've run.


Idling pressure has dropped to 35lbs according to the factory gauge as the miles have accumulated.Used to run at 40lbs hot idle.


31k total miles.


Blake
 

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Burner , I thought Champion Labs built both filters. I don't know why you saw a difference when changing brands of oil. All 15-40 or 5-40 should have the same viscosity at the same temperature when warmed up. My truck is an 02 and runs approximately 10 psi more pressure than two 03s and one 04 that I installed secondary filters on. Oil pressure is dependent upon a several things. I don't know if I even want to get into this because there is always someone that wants to nit pick my hydraulic lesson to death. To start with pumps don't pump pressure. They pump GPM or GPH. A typical rating for a hydraulic pump might be 10 GPM @ 1000 PSI max pressure. It is up to the manufacture to protect the pump/system form overpressure with a relief valve. Automotive pumps are a little different than other pumps because the speed of the pump is constantly changing as the engine speed changes. As the pump speeds up it pumps more oil that can leak out of the various bearings and orifices that spray oil around inside the engine. When this happens the pressure goes up to the relief valve setting in the pump. The pump has to be sized to allow for increased wear over the life of the system, different oil viscosity, cold starts etc. I don't consider our trucks as having a super high pressure lube oil system. GM did lower the pressure on the newer trucks. They must have decided they didn't need it to be that high. Maybe one of the Techs can tell us why. I haven't seen one of the pumps so I can only surmise that it is a positive displacement gear pump. I hope this wasn't more than you wanted to know. Later! Frank
 

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Discussion Starter #4
More info is always good. Ok, more GOOD info is always good.



Frank, the c5 Delvac 1 is 5w-40. I always listen to what you have to say, it's always good information.



I just got back from 3 dealers. I now have 2 black filters. The truck is "cooling" just a bit before the swap. I will install the filter with-in thirty minutes of this post and report back on my findings.


Burner---------->
 

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The truck is "HOT" and the pressure is right on, I mean exactly, 35lbs @ Idle or the mark just before 40. I don't know if it really makes any difference? .... FYI-- I added 1+ quart and started the truck. I allowed 4 minutes of idle time, just to make sure. I drove the truck really hard for about 1/4 mile and then parked to check pressure. It's about 75 here and the Attitude calls the motor temp @ 192.


Numbers........ Trans=150 Engine=192


Running test @ 20mph (1st gear) @ 2,500RPM yeilded 65-70 lbs and WOT=70-75lbs


So, in conclusion, I think that Frank is probably right.


I'll add one more post after a "morning" start.





Burner---------->
 

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Discussion Starter #6
I generally change my oil between 75 and 50% oil life. However, this time I wrung it out to 19%. Could this make a difference? I don't think it does.......but ya never know.






Burner---------->
 

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On note: There can be a big difference in oil temp between running solo and towing. The water temp gauge reading will be exactly the same in both conditions. My truck runs 3 to 4 psi less when towing in warm weather. I wish it was 75 here. I have a new VSD pump to install in my trailer. Later! Frank Edited by: Frank Blum
 

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NWDmax,


Is that really true that Wix makes Napa filters?


I'm about to go out and purchase some filters and my choices are from two parts stores. One sells Napa and the other sells Wix. (The Napa filters are a few dollars less.)
 

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Thats what I've always been told but see for yourself.
 

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Thanks Blake!


While you were posting I was out at the parts store and sure enough the filters I bought show the same as you posted!
 

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I cannot comment on the Dmax filters, but I did see a difference in pressure on my 6.0 gas between the Napa Silver & Gold filters. The Gold had less pressure. I was assuming that the Silver filter had a more restrictive element causing the addtional pressure.


I have always heard that it is cheaper to build a paper filter (air or oil) with poor flow quality and high filtration, as opposed to a paper filter that is less restrictive, but still meets mfg specs for filtration.
 

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The NAPA gold series is a better filter than the silver, although both are made by Wix. I changed oil in mine for the first time last weekend. First time since I have owned it that is. I'm not sure what oil was in it. I put in Rotella T synthetic 5w-40. The old filter was the black one, I switched to a NAPA gold. 38k on the truck, hot idle before and after is 37-38psi.
 

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Filter design will have an effect on indicated oil pressure. On my virgin oil with the Factory filter, my oil pressure would run about 60 psi @ 1800 RPM's. I changed the oil @ 1000 miles with Delvac 1300 and a Baldwin B1441 filter. The oil pressure is about 5 psi higher across the whole range when warm. (~65 psi @1800 RPM).


Frank is correct when he says a positive displacement pump is rated for a certain flow rate at a given speed. Positive displacement pumps, by design, will pump their flow rate to what ever pressure is required. (to a point).


Just a point of order Frank, the pressure regulator on a positive displacement pump is not normally called a relief valve. Both act the same but a relief valve is a safety device, not a design component.
 

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Lower pressure may indicate more filter surface area or a less restictive path after the filter media.


As long as the pressure is in the "normal" range I don't think it matters if its 5 pounds one way or the other



Blake
 

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I believe pressure relief is the right term when referring to an automotive oil pump. The valve is usually built into the pump. I have not seen a Duramax pump but I have changed the relief valve springs in a few Chevy SB pumps to increase the pressure. They were always referred to as such. We have something in common. I am a retired Mechanical Maintenance super. Later! Frank Edited by: Frank Blum
 

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If you look at the blue and the black filter from the top. You will see a lot bigger holes on the oem filter. They are of different design and make.
 

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STP filters are also made by Champion.
I got my last 2 on sale for $1.99 at Auto Zone.


BTW I never reset my Oil Life Monitor between changes, and it finally came on at 10157 miles.
 
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