20w-50 oil

duratothemax

duratothemax

<--- slippery roads
Aug 28, 2006
7,139
10
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Wyoming
Ive been running regular rotella 15w40 in my truck since new, but now im starting to notice my oil pressure is getting lower as the summer gets hotter. When I say low I dont mean low like what people normally complain about on duramax's (20-25 hot at idle)....I mean low like 16psi hot at idle if I get off the highway and come quickly down to a stop. My truck would only barely make the required 42psi by 1800rpm minimum spec as well.

I dont know why, maybe its because of the twins, maybe its because this engine was a GM test engine and god only knows what they were doing to it during testing etc....

When its really hot out, like 90*+, you can even BARELY hear, not really a knock, but just a unhappy 'really low oil pressure' sounding noise.

I wasnt due for an oil change, but the summer isnt getting any cooler so I had to at least try something. So I went to the auto parts store and got some 20w-50 and a new filter. Changed the oil and now I get 19psi HOT at idle after running it really hard and coming quickly down to a stop. If I let it sit and cool a bit Ill get a little more than 19psi. On the highway at 80mph I get almost 60psi and at 1800rpm I have a little under 50psi. Not as much as I would like, but its much better than before, and the engine doesnt make anymore expen$ive-sounding noises HOT at idle now. :)

All of these oil pressures are read from the tech 2/efilive.

Just my experience, thought I would share... :joker:

ben
 
wdino73

wdino73

Member
Sep 25, 2009
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Versailles, Ky
I run that Mobile 1 oil, but I've got a fresh engine with H series bearing, hot idle around 28 ish, 60 mph cruise, 65 ish, an cold pressure is off the guage, I do like this oil the engine does seem alittle quieter, than when I run Rotella in it. :thumb:
 
kman2468

kman2468

Old Man Truck
May 3, 2009
374
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33
wow my oil gauge is way off in my truck then.. i run at about half way between 0 and 30 in hot idle, and a about 45ish at 65...maybe this is what is causing my knock???
 
duratothemax

duratothemax

<--- slippery roads
Aug 28, 2006
7,139
10
0
Wyoming
the factory oil pressure gauge is accurate (it doesnt "lie" like some people might say the coolant temp gauge does) but its best to get an actual digital "number" reading with the tech 2 or efilive
 
Last edited:
wdino73

wdino73

Member
Sep 25, 2009
735
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Versailles, Ky
duratothemax said:
the factory oil pressure gauge is accurate (it doesnt "lie" like some people might say the coolant temp gauge does) but its best to get an actual digital "number" reading with the tech 2 or efilive
Click to expand...


I concurr sir, I have the digital temp gauge I don't trust the analog. LOL
 
duratothemax

duratothemax

<--- slippery roads
Aug 28, 2006
7,139
10
0
Wyoming
FWIW the factory low oil pressure warning (chimes and "OIL PRESSURE LOW" displays in the driver info center) comes on at 7psi. I raised the warning threshold in mine to 15psi just because.... You can do this with efilive.
 
wdino73

wdino73

Member
Sep 25, 2009
735
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Versailles, Ky
duratothemax said:
FWIW the factory low oil pressure warning (chimes and "OIL PRESSURE LOW" displays in the driver info center) comes on at 7psi. I raised the warning threshold in mine to 15psi just because.... You can do this with efilive.
Click to expand...

Thanks I didn't know that, that would give u a safety net, if I'm understanding that correctly??
 
05smoker

05smoker

I'm officially done!
Mar 30, 2007
2,379
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Lebanon, OH
I don't remember what diff it made when I was running Cenpeco 20w-50 vs 15w-40 in my LLY (any little bit helps in an LLY:() but it did add a few psi when warm. I might actually go back to it this next change and can chime in again then. I ran Mobile 1 once and never again. I believe in it in my gassers but it was too thin. Only time my Dmax ever used a noticeable amount of oil between changes.

Anyone ever conclude why the LLY is so much lower than the LB7?? My LB7 with 157k on it would damn near peg it at start up and then hover at 40psi most of the time.
 
wdino73

wdino73

Member
Sep 25, 2009
735
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55
Versailles, Ky
05smoker said:
I don't remember what diff it made when I was running Cenpeco 20w-50 vs 15w-40 in my LLY (any little bit helps in an LLY:() but it did add a few psi when warm. I might actually go back to it this next change and can chime in again then. I ran Mobile 1 once and never again. I believe in it in my gassers but it was too thin. Only time my Dmax ever used a noticeable amount of oil between changes.

Anyone ever conclude why the LLY is so much lower than the LB7?? My LB7 with 157k on it would damn near peg it at start up and then hover at 40psi most of the time.
Click to expand...

I'm my humble opinion the LB7's have a better bottom end an I think that's why they hold better oil psi. IMO
 
kman2468

kman2468

Old Man Truck
May 3, 2009
374
0
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ok heres the oil while engine was hot. it peaked at 48 because i was accelerating but going about 60 it was about 45.6
oilpsi.jpg
 
Diesel Pilot

Diesel Pilot

Hat? Suitcase? 50 BMG?
Aug 9, 2006
1,424
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Pickerington, OH
05smoker said:
Anyone ever conclude why the LLY is so much lower than the LB7?? My LB7 with 157k on it would damn near peg it at start up and then hover at 40psi most of the time.
Click to expand...

It's cause LLY's are like the Fonz, calm and collected. Like a person having low blood pressure under stress. Every things cool man. :cool2:

duratothemax said:
definitely noticed an improvement in acelleration and turbo spool too.
Click to expand...

I'm skeptical of this claim. Is this like seat of pants meter stuff. I fail to see how changing oil grades helps the turbo spool better. Enlighten me, please. No KB style breakdowns either. ;)

wdino73 said:
I'm my humble opinion the LB7's have a better bottom end an I think that's why they hold better oil psi. IMO
Click to expand...

:spit:
 
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