GM aborting move to 0w-40

Snagglefoot said:
Nothing much here. A secret US auto worker bad mouths a Mexico based manufacturer. Yawn. Let’s get those cranks mic’d and compare them to the specs. Otherwise it’s just finger pointing.
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Two latest GM Bulletins mention some surface finish and dimensional issues as “root causes”. Hmmm nobody asked 5 why’s?
 
Thickies had a good 4 day long party. Thickies finally felt that their point of “thicker is better” was finally followed by one of the domestic big three’s that are heavily monitored and controlled by our favorite gov agency, the EPA. It probably felt very empowering.

But all jokes aside, sadly this whole GM l87 fiasco exposed that GM couldn’t just bandaid a problem with thicker oil. Manufacturing defects are defects that cannot be corrected just by changing viscosity…. Engine replacements is the right move for GM, but I just hope the new replacement engines are actually better than the bad date code engines. only time will tell.
 
ARCOgraphite said:
Thinking out loud:
You think the U.S. engine assy post assembly spin test would "see" undersized crank pins on the press/volum plot. Maybe they are O.O.T. oversized. Then again the spin test should see at least an interference in the spin-up torque reading, though it would likely not see a 0.0005" diametrical clearance (which will be << 0.0003" running).

Incoming QC sampling should have caught a batch of out of tol. cranks. Before that, the outsource factory automated tools would have caught it right away if programmed properly. Did GM Autodesk Fusion send some funky #'s? Was it a pandemic world crash and burn all around? Starting to smell like a big ball drop.
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agree ,its strange , with all the qc, iso 9000 yada yada , that goes on that something like this wasnt caught all this time ? im tool and die maker , working to .0001 inch on daily basis , i would almost believe there was some numbers wrong in there inspection process, or in the blueprints/ cad models that lead to this , maybe a corner rad on rod journal that was just out of spec ,
we build cells and testers that go into auto assembly plants,there are a lot of protocals designed into these stations that idiot proff the whole process , so assemblers can dam near never get something wrong , i have been following some of this info coming out of forums ,and stuff , it would be very interesting to really find out , exactly what the the final culprit is ,and how it happened, but im sure that wont happen
 
xmanjeff said:
agree ,its strange , with all the qc, iso 9000 yada yada , that goes on that something like this wasnt caught all this time ? im tool and die maker , working to .0001 inch on daily basis , i would almost believe there was some numbers wrong in there inspection process, or in the blueprints/ cad models that lead to this , maybe a corner rad on rod journal that was just out of spec ,
we build cells and testers that go into auto assembly plants,there are a lot of protocals designed into these stations that idiot proff the whole process , so assemblers can dam near never get something wrong , i have been following some of this info coming out of forums ,and stuff , it would be very interesting to really find out , exactly what the the final culprit is ,and how it happened, but im sure that wont happen
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It seems lately that everyone with a cell phone on a stick is a YT content provider. Sadly most of them wouldn’t have a clue what you are talking about.
Back in the day I had several SBC and BBC engines rebuilt. The machine shop would ask me what I wanted for bearing clearance. Always the same, 10/10 and two and a half on both rods ‘n mains.
That was about half a thou more than factory specs.
More bearing clearance reduced MOFT, which meant a 10w30 with a HTHS of 3.5 was the minimum engine oil viscosity in those engines.
I always used high volume oil pumps with the high pressure spring installed to make sure that the bearings furthest from the pump got an adequate oil supply.

I’m not buying Mexican crankshafts in the 6.2s were polished wrong, had sand in them or were somehow defective, but were .00025-.0005 under size which increased bearing clearances.
Increased bearing clearances require an increase in oil viscosity.
 
Always something...

1747836827574.webp
 
Oh boy....haven't watched yet.

*Important Note!* I asked a GM powertrain engineer directly about this, who spends his life living and breathing modern performance engines (and specifically small block V8s). Regarding the L87 engine discussed in this video, I asked directly if today's modern, thinner engine oils are too thin for enabling reliability and cause concern of additional engine wear. His answer was a very concise "no." Testing validates this. I think if you watch this video fully (which is quite information dense!), you'll come to understand why. The blame does not lie on the engine oil, as the video breaks down in great detail. Did a lot of research for this one - hope you enjoy it!!



1748014523036.webp
 
buster said:
Oh boy....haven't watched yet.

*Important Note!* I asked a GM powertrain engineer directly about this, who spends his life living and breathing modern performance engines (and specifically small block V8s). Regarding the L87 engine discussed in this video, I asked directly if today's modern, thinner engine oils are too thin for enabling reliability and cause concern of additional engine wear. His answer was a very concise "no." Testing validates this. I think if you watch this video fully (which is quite information dense!), you'll come to understand why. The blame does not lie on the engine oil, as the video breaks down in great detail. Did a lot of research for this one - hope you enjoy it!!



View attachment 280766
Click to expand...

Under the majority of operating conditions, which is what these recommendations cater to, he's right. Though I do note the use of the word "significant" in the quote, which, since it's included, leads one to infer that there was in fact an increase, but it wasn't significant. This takes us back to the Honda paper and "acceptable" wear control, which is the name of the game. If wear can be kept to an acceptable level, over the life of the equipment, while viscosity is reduced to improve CAFE figures, then it's win-win for the OEM and likely inconsequential to Joe Average.
 
factorytuned2012 said:
What’s wrong with a good ole 5w30?
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Nothing. Manufacturers went to 0W because it helps their fuel economy numbers. The warm-up cycle is where they lose a lot of efficiency. That and perhaps simplification since you can then recommend the same oil to both Alberta and Arizona.
 
chris719 said:
Nothing. Manufacturers went to 0W because it helps their fuel economy numbers. The warm-up cycle is where they lose a lot of efficiency. That and perhaps simplification since you can then recommend the same oil to both Alberta and Arizona.
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Then give it a 0w30 if they’re that concerned
 
chris719 said:
Nothing. Manufacturers went to 0W because it helps their fuel economy numbers. The warm-up cycle is where they lose a lot of efficiency. That and perhaps simplification since you can then recommend the same oil to both Alberta and Arizona.
Click to expand...
So then 0w-30 it and again, win all around.
 
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