A “heavier” oil will cause higher oil temps though right? So does it really offer better protection? Or is the trade off still worth it
Which oil would you choose? Seeing specs only
- Thread starter bherriman
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Yes, the 40w oil still provides “better protection.” The recommendation for my truck is a 10w30 or 5w40 oil, (won’t get into approvals) but I opt for the 40w due to its enhanced protection, considering it’s a large diesel engine. Although your truck is a smaller displacement version, it still generates a substantial amount of power.
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A tiny increase in the bearings which is inconsequential.
10 to 20%
All these years, I thought the grade was a rough representation of viscosity. Turns out it's a protection factor. 40 grade has twice as much "protection" as a 20. Learn something new on BITOG every day.
What are we protecting against?
Uhhh the hths is much higher in a 40w vs 20w……..protection against excessive heat, fuel dilution, and the loads a diesel usually hauls. You want to run a 20w, with a much lower hths, in your diesel? Are you saying class 8 trucks should use a 20w?
Also moft
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Everybody's favorite Oil Geek told me in an email after sending multiple VOA samples to SD while looking for "the best" oil for the Audi:
"I will say that virgin oil analysis does not predict actual engine performance."
"I will say that virgin oil analysis does not predict actual engine performance."
This is true, but knowing the HTHS of an oil can aid in making informed decisions and doesn’t require a VOA. HTHS is a critical parameter for determining how well an oil maintains a “protective film” between moving parts under extreme heat and stress, which ultimately impacts engine longevity/durability. The higher the viscosity ( 20/30/40, etc.), the higher the HTHS, which, in the words of @bherriman, provides better “protection”. In this case, it’s a 40w for his 3.0 Duramax.
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Completely agree, and would use data from manufacturers' SDS for their HT/HS and other specs in helping determine the correct oil for my usage, supplemented with data I could find from other sources, e.g. some oils are more prone to viscosity changes over time than others.
I referenced this quote from LSJr because others had commented on VOAs and UOAs. He also told me just because an oil's VOA doesn't look as good on paper compared to others, doesn't mean it won't perform as good or better.
Of course not.
I would use the grade/HTHS (and more importantly, ratings) that is/are appropriate for the machine. As I do for my diesel and passenger cars. And you're going to have to school me on how HTHS protects against heat. As far as I'm concerned, HTHS doesn't measure the ability of the oil to carry heat from piston gallery to my oil cooler.Uhhh the hths is much higher in a 40w vs 20w……..protection against excessive heat, fuel dilution, and the loads a diesel usually hauls. You want to run a 20w, with a much lower hths, in your diesel? Are you saying class 8 trucks should use a 20w?
Your first point was that grade = "protection".
Now your point is that grade = hths, which is [only] loosely true.
I guess we should 20w-50 all the things?
Has the 3.0 duramax shown itself to be prone to mechanical failures? Wiping cams? Main/rod bearings? I'm not aware of that trend, so I'm not sure why anybody should jump on the HTHS bandwagon so hard that they want to jump ship on C3 oils and go straight to "full saps" CJ/CK-4. It's a european passenger car diesel designed as such.
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I quoted the term “protection” that @bherriman used. Hence the reason I used quotes in my reply if you care to actually read my post and not selectively dissect points you wish to conflate. And by using a 40w you are using an oil with a higher HTHS. So in turn, yes, using a thicker viscosity which in turn has a higher HTHS would ensure adequate minimum oil film thickness under severe use such as high ambient temps, elevated oil temps seen when towing heavy, etc. There would be zero issue using a 5w40 in the 3.0 Duramax despite GM recommending a 0w20 Dexos D oil. I certainly wouldn’t use 0w20 in that engine if it were mine. I hope that clears things up as it seems you are misconstruing the point I was making. Therefore, using a 40w oil instead of a 20w in a diesel engine that is used like a truck would be a wise choice. HTHS viscosity measures how an oil behaves under severe use conditions of an engine in use, specifically at high temperatures. I said “protection” from excessive heat. I didn’t say that HTHS “carries heat” you’re putting words in my mouth.
PS: 20w50 would be fine if it’s used in an appropriate winter climate. Maybe not necessary, but totally fine.
If HTHS doesn't protect the engine from heat, and HTHS doesn't protect the oil from heat, I can't imagine what we imagine it's doing.
FWIW, the dexos spec specifies HTHS. Grades don't.
Did you not read my previous post? On that note, I see that you’re unable to comprehend what I’m posting and I’m done conversing. Have a nice day.
If we think every vehicle for which the manual specifies anything less (numerically) than 15w-40 is going to die a premature death, and thus decide to worship at the altar of maximum HTHS for all the things, we are headed down the path of ignorance.
Last I checked, light duty truck diesels are dying of head gaskets, hung injectors, CP4 grinders...more often than wiped cams and main bearings. Well, 2019+ rams aside.
0w-20, 5w-20, 0w-16 (gasp) death swill be banished.
So this is just about your aversion to using thicker than specified viscosities; noted. You could have saved me a lot of typing stating this from the beginning. I care about engine longevity, not 0.01mpg. To each their own.
On the other hand there's no real reason not to use a higher grade if you wish, other than a truly tiny increase in fuel consumption. If that's your one and only goal then go for it, but it's not as if the thinner grades are "good" for the engine or somehow beneficial in a mechanical sense.
People worship at the altar of thinner grades too when there's no real technical reason so do so other than fuel consumption. Any engine that has design changes to allow it to tolerate thinner grades won't be adversely affected by a higher grade. On my Tiguan I appreciate the buffer a 504 00 oil gives for fuel dilution.
I don't disagree...as long as I'm not doing something silly in terms of cold starting or chemistry (which includes SAPS considerations for DPF.) It's just silly to insist that viscosity is the only thing that matters if clearly there are other factors that matter too. Two of my three vehicles are running a grade higher than the oil cap denotes and the other gets 15w-40 summer, 5w-40 winter CK-4. I'm just not pretending that I'm "protecting" things any better from anything. What benefit would we really expect to see by dual-rated 15w-40ing all the things?
If I had a babymax, I'd run a WM available C3 rated oil in it and I wouldn't sweat the difference between 5w-30 and 5w-40. That likely would shake out to be ESP 5w-30. It's a car engine with a thermostatically controlled oil cooler.
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rotella 0w40
You are protecting it. Increased HT/HS always reduces wear, it is not linear but it's always an increase. The winter rating takes care of cold starting, any oil with a 0W winter rating will pump at temperatures of -35 or even below.
I agree that ESP in a 30-grade is a great oil, nearly a universal oil for most engines. Reduced SAPS and a minimum HT/HS of 3.5. I use it in every vehicle now that it is available at Walmart for a very good price.
Branson area here
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