0-20w oil

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B-train

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Is it possible to be more specific about which motor oils GM recommends for the 6.6L L8T, besides just '5W30 synthetic'?
Are there any unique standards called out, above & beyond '5W30 synthetic'?
I don't believe there are any unique standards. Just 5w-30 Dexos oil is called out. Same oil as specified for the 6.0L gas motor in the previous HD line.
 

Marky Dissod

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The 6.6L L8T will accept ANY 5W30 Dexos motor oil? REALLY?
Find it hard - but not impossible - to believe. But if true, deeply disappointing.
Was hoping for more specificity on GM's part.

My budget and time constraints force me to settle for
0W20 / 0W30 / 5W20 / 5W30 Group IV synthetic -
but I'd still like to know how far down I'm stooping.

Stopping at 'good enough for GM's recommendation' always left a bad taste in my mouth.
It irked me that the LT1 in sedans / wagons called for 'whatever 5W30 you find'
but the nearly identical LT1 in the 'vette of the same years not only specified synthetic 5W30,
it only allowed 5W30 that passed the 'GM 4718M' standard.

Was hoping the L8T had a higher standard than lesser EcoTec engines.
 

BlaineBug

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Here’s a copy of a GM warranty from 1970. 12 months /12k miles BTB,5/50 powertrain. Still think warranties were better 50 years ago?


View attachment 360129
Compare and contrast the price of that 1970s vehicle versus the similar equal of today, accounting for today's actual inflation (not the gimmicky fake news inflation numbers produced by mainstream propaganda media outlets) and let us just see how awful that 1970 warranty turns out to be. I wonder.....
 
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Antonm

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Having been an engineer for one of the major OEMs, I can assure you that the voices of accountants and regulatory compliance officers are heard FAR more than that of engineers.

Its hilarious reading this thread, everyone talking "it was designed and engineered to run X oil", um no, no it wasn't. There hasn't been a totally new design in at least several decades, probably more (because why would you spend all that time on R&D money on something you already have), every new motor design is a copy /paste of a preexisting engine (one that the parent company has licence for) and then its modified to meet whatever new requirements' exist, at the cheapest possible cost, using only parts/ components' / lubricants from preferred suppliers.

I've personally had a situation where the clear, obvious, much better engineering choice was readily available at a very negligible price increase. Guess what, this major OEM used the slightly cheaper option from a preferred supplier because the MBA's make the final calls, not the engineers.

I know this is a diesel engine thread, but just as an example take the gasser 6.2 used in Tahoe/Yukon/Escalade and compare it to the 6.2 gasser found in the Corvette. They are more alike than they are different. The oiled components are identical, but GM say to use 0W40 in the corvette and 0W20 in the Tahoe/Yukon/Escalade. Nothing is different about the reciprocating assemblies between the engines, yet GM recommends two different oils. Why, because of CAFE, no other reason, the thinner oil is not better for anything other than helping GM meet a regulatory requirement.
...
 
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BlaineBug

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Having been an engineer for one of the major OEMs, I can assure you that the voices of accountants and regulatory compliance officers are heard FAR more than that of engineers.

Its hilarious reading this thread, everyone talking "it was designed and engineered to run X oil", um no, no it wasn't. There hasn't been a totally new design in at least several decades, probably more (because why would you spend all that time on R&D money on something you already have), every new motor design is a copy /paste of a preexisting engine (one that the parent company has licence for) and then its modified to meet whatever new requirements' exist, at the cheapest possible cost, using only parts/ components' / lubricants from preferred suppliers.

If personally had a situation where the clear, obvious, much better engineering choice was readily available at a very negligible price increase. Guess what, this major OEM used the slightly cheaper option from a preferred supplier because the MBA's make the final calls, not the engineers.

I know this is a diesel engine thread, but just as an example take the gasser 6.2 used in Tahoe/Yukon/Escalade and compare it to the 6.2 gasser found in the Corvette. They are more alike than they are different. The oiled components are identical, but GM say to use 0W40 in the corvette and 0W20 in the Tahoe/Yukon/Escalade. Nothing is different about the reciprocating assemblies between the engines, yet GM recommends two different oils. Why, because of CAFE, no other reason, the thinner oil is not better for anything other than helping GM meet a regulatory requirement.
...
I never knew that, that 0w40 is the recommended weight for the Corvette 6.2. Simultaneously, I was never of the thought process that the motors were any different!
 

Antonm

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I never knew that, that 0w40 is the recommended weight for the Corvette 6.2. Simultaneously, I was never of the thought process that the motors were any different!

There are some differences in the fuel injection systems, the computer tuning is decently different from what I understand ( I’m not knowledgeable enough about the computer tuning in either, just what I’ve heard), belt drive and such. They’re very similar but not identical, and you could take either one and convert it into the other from a mechanical standpoint.

The important part for an oil discussion is the crank and cam bearing clearance specs, which are the same between the truck 6.2 and corvette 6.2, yet GM says they take different oils.
 

Marky Dissod

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Having been an engineer for one of the major OEMs, I can assure you that the voices of accountants and regulatory compliance officers are heard FAR more than that of engineers.
...
I know this is a diesel engine thread, but just as an example take the gasser 6.2L used in Tahoe / Yukon / Escalade,
and compare it to the 6.2L gasser found in the Corvette. They are more alike than they are different.
The oiled components are identical, but GM says 0W40 in the corvette and 0W20 in the Tahoe / Yukon / Escalade.
Nothing is different about the reciprocating assemblies between the engines, yet GM recommends two different oils.
Why? Because of CAFE, no other reason.
The thinner oil is not better for anything other than helping GM meet a regulatory requirement.
This explains A LOT.
So far as I'm concerned, this is why I'd use 0W30 or 5W30 instead of 0W20 or 5W20.
(Don't think I drive hard enough to NEED 0W40.)
By the way, what kind of 0W40? I'm not a tribologist, but I know that not every 0W40 is identical to any other 0W40.
There are some differences in the fuel injection systems, the computer tuning is decently different from what I understand
(I’m not knowledgeable enough about the computer tuning in either, just what I’ve heard), belt drive and such.
They’re very similar but not identical, and you could take either one and convert it into the other, from a mechanical standpoint.

The important part for an oil discussion is the crank and cam bearing clearance specs, which are the same between the truck 6.2L and corvette 6.2L -
yet GM says they take different oils.
This is why I asked about the oil specified for the 6.6L L8T, as opposed to the lesser EcoTec V8s that are subject CAFE MpG test standards.
 

15burban

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From my research the 0w40s especially pennzoil ultra platinum for the 6.4 srt's (challengers, chargers, ram 2500 and 3500) after a few thousand miles the oil shears down to a 30 weight. I don't know the scientific reason other then since it is such wide range going from a 0 (cold) to 40 (hot). That's based on uoa's from Blackstone I've seen. I run redline 0w30 in the winter and am going to be running redline 5w30 in my 16 6.4 ram. Redlines 30weight is a really "heavy" 30weight, border line 40 weight but doesn't shear down very much. So if I ran 0w40 pup in it for 5k miles it would be thinner more then likely somewhere between 2-3k mile mark up to 5k then the same 5k mile interval with 5w30 that is more shear stable. At least with redline oil.

Another non gm fun fact. On the Rams with the 5.7 hemi in the past couple years they switched from recommending 5w30 to 0w20. From 09 to now nothing has changed with that motor. It's all to appease the epa and claim .00001 mpg better.

Sorry about the non gm talk. For our 5.3 it will always get 5w30. This last time I picked up 3 5 gallon jugs of pennzoil ultra platinum 5w30 from Walmart for $79. Enough for almost 2 oil changes so I'll order more when needed. Not dexos rated and I could care less if it is or isn't.

Toyota has a 0w8 oil. Pretty soon we will just be filling up our engines right out of the spigot.
 
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