Only (2) choices in synthetic 15W40?

PACougar

PACougar

Active member
Jun 27, 2012
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El Dorado Hills, Ca
I don't see any reason to run a 15w40 over a 5w40. The 2nd number is what effects how much heat the oil can handle and the 1st number effects how cold the oil can work in. 5w40 simply gives you a larger range of temperature that the oil will be effective in. For the record I run Schaeffer's 9000 Supreme 5w40 in both of my trucks. You can pick up 5 gallons on Amazon for around $143.00 shipped with Prime.
 
496 BB

496 BB

Head Thread De-Railer
Feb 20, 2009
697
5
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At your girlfriends house
So for summer a 5W40 wont lower psi at idle? IDK Im just asking cause on my 8.1L I went to 10w30 instead of 5w30 to get oil pressure up to where I liked it. Big difference on it.

What thoughts on this post from BITOG? May have been from Idaho Rob as his screen name was BoiseRob....or maybe not.

ozzman,

There had been many discussions about piston failures in the Duramax engines at the Diesel Place and other Dmax websites. One of the common symptoms was reduced oil pressure under load due to heat. Several owners noticed that right before their piston failures while under load, the oil pressure had dropped to 20-25 psi. Unfortunately, the piston squirters in the Dmax flow when the oil pressure is 29 psi so they felt that the pistons suffered heat damage due to the lack of oil cooling on the bottom of the piston.

Although synthetic oils flow better when cold, they also don't "cling" as well as group III dino oils due to their molecular structure. I am hoping to avoid the heat stress to my pistons by using a high quality group III oil like Schaeffer #151.

I can tell you one effect I notice right away. My idle oil pressure with Supreme 9000 was around 25 psi. Supreme 7000 maybe 1-2 psi higher but Scheaffer's #151 is showing an idle oil pressure of 30 psi which means my piston squirters are still flowing at idle. \:\!

Thanks for asking...

Rob

I dont buy the syn is worse than dino argument but what about the coolers? Im still diesel retarded remember...lol.
 
mike diesel

mike diesel

I'm alright.
Sep 6, 2012
4,005
0
36
SLC, Utah
PureHybrid said:
Sludge in the turbo aka oil coking is from shutting it down while exhaust temps are too hot (350°+).

I'm not a real believer in synthetic oils, especially with the limited amounts that have to be synthetic for it to be labeled so.

When I worked at the cummins tech center, they ran Premium Blue 15/40 (obviously), and those engines are put through hell, with higher oil temps and coolant temps only a moron would run it to in a pickup. After a hotbox test engines would get torn down, and the only thing wrong is usually abnormal carbon in the ring lands. But that's what you get running oil at 280°F for 250hrs.

In my personal truck with 220k, I've ran Delo; Delvac; Rotella t6 and regular; Premium Blue and Amsoil one time. Only difference I've ever noticed was the smell coming from the blowby tube. Motor was still clean inside when I peeled it open to check lash. Been running Delvac for the last 2yrs, its great oil and its usually the cheapest at Rural King.
Click to expand...

Your first statement....I dont necessarily agree with it. Considering gas engines idle at 900°+ and you typically don't hear about coking issues. You'd think that every turbo gas engine on the planet would freeze up solid with sludge shutting them down around 900°, let alone 350+.
 
Harbin_22

Harbin_22

Active member
Dec 4, 2010
3,858
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Southern Indiana
mike diesel said:
Your first statement....I dont necessarily agree with it. Considering gas engines idle at 900°+ and you typically don't hear about coking issues. You'd think that every turbo gas engine on the planet would freeze up solid with sludge shutting them down around 900°, let alone 350+.
Click to expand...

I've always wondered why people let these idle before shutting off for the reason exactly. I've had turbo gassers and you are right.
 
Chevy1925

Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
21,278
5,162
113
Phoenix Az
496 BB said:
So for summer a 5W40 wont lower psi at idle? IDK Im just asking cause on my 8.1L I went to 10w30 instead of 5w30 to get oil pressure up to where I liked it. Big difference on it.

What thoughts on this post from BITOG? May have been from Idaho Rob as his screen name was BoiseRob....or maybe not.

ozzman,

There had been many discussions about piston failures in the Duramax engines at the Diesel Place and other Dmax websites. One of the common symptoms was reduced oil pressure under load due to heat. Several owners noticed that right before their piston failures while under load, the oil pressure had dropped to 20-25 psi. Unfortunately, the piston squirters in the Dmax flow when the oil pressure is 29 psi so they felt that the pistons suffered heat damage due to the lack of oil cooling on the bottom of the piston.

Although synthetic oils flow better when cold, they also don't "cling" as well as group III dino oils due to their molecular structure. I am hoping to avoid the heat stress to my pistons by using a high quality group III oil like Schaeffer #151.

I can tell you one effect I notice right away. My idle oil pressure with Supreme 9000 was around 25 psi. Supreme 7000 maybe 1-2 psi higher but Scheaffer's #151 is showing an idle oil pressure of 30 psi which means my piston squirters are still flowing at idle. \:\!

Thanks for asking...

Rob

I dont buy the syn is worse than dino argument but what about the coolers? Im still diesel retarded remember...lol.
Click to expand...

i notice no difference at idle pressure from the 15w40 dino oil to the 5w40 full syn i run in the summer. both idle at 27ish psi at 200* and still push 60psi at 2100rpm at 210*.

thats on a built motor with a stock oil pump and clearances a touch to the loose side from stock setting on the mains and rod bearings
 
PureHybrid

PureHybrid

Isuzu Shakes IT
Feb 15, 2012
3,357
388
83
Central OH
mike diesel said:
Your first statement....I dont necessarily agree with it. Considering gas engines idle at 900°+ and you typically don't hear about coking issues. You'd think that every turbo gas engine on the planet would freeze up solid with sludge shutting them down around 900°, let alone 350+.
Click to expand...

Not my findings, CTT engineers.

And, oil temps on a gasser just driving around town aren't that high, same with a truck. If you are towing and the engine is heat soaked (not just high EGT from a quick run), and you don't let it cool down, the turbo among other parts will hate life.
 
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THEFERMANATOR

THEFERMANATOR

LEGALLY INSANE
Feb 16, 2009
3,890
43
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43
ZEPHYRHILLS, FL
Only real difference I noticed was the lack of a typewriter tick with 5w40, lower oil pressure when cold, and much faster crankong rpm's with my smaller batteries. I still hold 28-30 at a hot idle, and have no problems hitting the bypass pressure running down the road. I will say rptella t6 5w40 holds less oil pressure on a cold start, but more at a hot idle than mobil 1 5w40 synthetic did. I ran the mobil 1 for 2 changes, and when I went back to rotella my hot idle oil pressurecame back up to 30 from 25 with the mobil 1. Also the mobil 1 would run 70-75 psi on a cold start where the rotella runs 65-70. So I prefer the rotella synthetic(even though I know its not a true synthetic base stock) for lower cold oil pressure, but higher hot oil pressure.
 
496 BB

496 BB

Head Thread De-Railer
Feb 20, 2009
697
5
18
43
At your girlfriends house
Getting some Schaeffers tomorrow. Thanks for all the info.

Anything special with rear diff fluids I should know about? Thinking Schaeffers on that too if they have it at NAPA where Im getting oil tomorrow. The 741 fluid I think.

Also are the Delco oil filters good?
 
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