LML Oil Pressure Variance???

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I did my 3rd oil change since 14k miles using Amsoil 15w40 Signature Series and EAO52 filter so far just using the oil life monitoring system. The oil pressure has been consistent 21psi hot idle and 40psi cruising at 60mph. I've had I bought the truck with 9k miles and first change the oil to Rotella T6 and Mobil 1 oil filter with same oil pressure results using my CTS2 monitor. The other night I changed my oil for the 3rd time using Amsoil and notice now oil pressure at 22psi hot idle and 45psi cruising on the highway also the truck feels to have an increase in power. So why would my oil pressure be higher now on the 4th oil change? I switched to Amsoil because I wasn't happy with the Rotella T6 I noticed a little oil coming from my exhaust and a puff of white smoke on startup but haven't experienced any of this with the Amsoil. Did I get a bad filter or possibly the the engine is broke in now with 33k on it. I also noticed my operating temp is a couple degrees lower too now.
 
I 100% agree but the temp just dropped a little this morning. We had the same temperature drop on the last oil change and it was ineffective. I'm just curious how do you know if your oil filter is in bypass or even bad?
 
Oil filter by-pass's internally when media won't flow the volume being pumped. Two ways to play this game. Filter with higher internal by-pass built-in, or bigger filter with more media area so it never sees enough restriction to cold oil to open the by-pass in the first place
smile.gif
 
Totally coincidental. Oil pressures will always vary a bit. The oil will only be "thinner" when it's cooler outside because it will take a little bit longer to warm up. Once up to full op temp it will be controlled by the oil cooler which uses the engine coolant to control temps.

Also, oIl filters rarely ever go into BP, and when they do, it's only for a VERY short time (less than a few seconds) at cold start up. Once the oil pressure comes up in the full system, the dP across the filter is far less than the overall operating pressure, and never close to the filter BP crack-open. This has been proven (data logging experiments from Jim Allen) elsewhere on this site. Typically oil filters can flow WAY more than the engine will pump, as a safety design feature so as to not induce a media rupture.


What I don't understand is why folks worry about this stuff; it's minutia and is no indication of anything going right or wrong.
 
Dnewton I wasn't necessarily worried as much I was curious? I was wondering if there was a difference in the oil enough to bring a 5 psi difference driving 60 or mabey even an issue or difference in the filters?
 
No problem. It's really just too hard to compare/contrast such small nuances without understanding all the variables.

As a fellow Dmax owner, the wear rates are so low and consistence, I guess curiosity about oil pressure is about all we have to talk about!

And unless you're running extended OCIs, just ditch the syns; big waste of money.
The Dmax is the best wearing light-duty diesel engine in modern times. Simply impeccable wear traits. Using a syn does nothing to improve the already great wear rates.
 
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I have a 2013 Duramax and have the EZ Lynk setup. Warmed up here in Texas my pressure will run around 22 psi at idle and 44 driving. First start up in the morning the pressure at idle can be as high as 62 psi. I'm currently at 53K miles and I use Mobil Delvac 15w-40 I buy at Wally World.
 
Hasty what I was getting at is my oil pressure was higher for the first few hundred miles after an oil change then the average dropped a bit with no difference in outside temperatures.
 
Hasty your saying its the same with Mobil Delvac conventional 15w40 and Amsoil 15w40? If so are you also running the Amsoil filter? This last change I did 1500 miles ago with conventional 15w40 and donaldson filter and my pressure has been the same so far.
 
oil viscosities are spec'd @ 40C + 100C + vary from there. base oils that are real synthetic-group IV + V which there are few will thicken less + slower under the 40C spec + they will thin less over the 100C spec. this could effect oil pressures both warm + cold!!
 
Never used an Amsoil filter, I use M1-303 or B1441. I have run both filters with Mobil Delvac conventional 15w40 and Amsoil 15w40 OE/Heavy Duty oils. Temperature stays warm to HOT in this part of the country so not much experience beyond a very rare 32 and below start up when my pressure will jump up to 79-80 then drop down to normal once the oil is warmed up.

I have never noticed the slight difference after a change like you have noted.
 
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