The folks at Corvette Forum have done a good job explaining:
https://www.corvetteforum.com/forum...921439-6-2l-engine-recall.html#post1608776331
Video - Engineering Explained, Do Thin Oils Destroy Engines?
- Thread starter martinq
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The folks at Corvette Forum have done a good job explaining:
https://www.corvetteforum.com/forum...921439-6-2l-engine-recall.html#post1608776331
"Why the LT2 Avoided the L87’s Recall Issues
• Manufacturing Window: The L87 recall is tied to a specific production period (March 1, 2021–May 31, 2024) with defective components from suppliers. The LT2, produced for the lower-volume Corvette, likely used different batches or suppliers, or benefited from stricter quality control. GM’s 2025 L87 engines are also exempt from the recall due to manufacturing improvements, suggesting the LT2 may have been built with similar or better processes.
• Oil Viscosity: The LT2’s use of 0W-40 oil from the factory aligns with GM’s recall remedy for the L87, indicating that higher-viscosity oil may reduce bearing wear. The L87’s initial 0W-20 specification may have exacerbated issues in defective engines.
• Application Differences: The LT2’s dry-sump system and performance-oriented design reduce stress on components during high-RPM operation, unlike the L87’s wet-sump system, which faces different load patterns in truck applications (e.g., towing).
• Production Scale: The Corvette’s lower production volume (tens of thousands vs. nearly 600,000 L87-equipped vehicles) means fewer opportunities for defective components to affect LT2 engines, and GM may prioritize quality for its flagship sports car.
Conclusion
The LT2 V8 in the 2025 Corvette differs from the L87 V8 in GM’s recalled trucks and SUVs through its performance-oriented design (dry-sump, shorter intake runners, higher horsepower), use of 0W-40 oil, and apparent exemption from the manufacturing defects affecting L87 engines from 2021–2024. The L87’s recall stems from faulty connecting rods and crankshafts, leading to engine failures, while the LT2 has no reported similar issues, likely due to different production processes or quality controls. Owners of L87-equipped vehicles should check their VIN on GM’s recall lookup website for inspection and repair details, while Corvette owners can rest assured the LT2 is unaffected by this recall."
Yep, I suppose its a "tolerance stacking" of various issues and conditions. Number produced, where they were produced, the actual use cases, etc.
If anything it helps lend credence to the "hand built" aspect of a Corvette.
Looking at the recalled engine Eric tore down, Im not sure oil weight would fix the issue. I suppose at best it could slow down complete failure, which may be what GM is trying to do (so they have time to produce replacements)
If anything it helps lend credence to the "hand built" aspect of a Corvette.
Looking at the recalled engine Eric tore down, Im not sure oil weight would fix the issue. I suppose at best it could slow down complete failure, which may be what GM is trying to do (so they have time to produce replacements)
I didn't like how the hone was gone in the cylinders on a less than 90k mile engine, and that IS a viscosity issue.
What I can't comprehend is that failures happened as soon as 4 miles after delivery, yet there was no fix in manufacturing for over 3 years. Even if GM would chance it on engines already sold, can't believe they never found the root cause.
I believe the issue is 6 of one, half a dozen of another...
It seems like they found the cause, eventually. They know exactly what VINs have "bad" engines but seem to be keeping a tight lid on the exact list (or maybe there are so many it would be a pain to publish in a bulletin)
Classic case of "let's sweep this under the carpet and hope we can get away with case-by-case basis", but that didn't work out.
Honda/Acura did this with their 4 and 5 speed automatic trans (attached to V6 engines) from 2000-2003 model years. I had 3 of them die in 2 different vehicles, yet other people had zero issues. They covered them all, including the 3rd which was well outside of warranty, but they never recalled them all...it was easier and cheaper just to hope and pray and cover each one at a time.
It seems we have forgotten how to build quality engines. As silly as that sounds, it rings true. There are engines built during WWII that were known for lasting a very long time, in some of the worst conditions, and would reliably stand up to 2 times the original output when used in racing applications.
Rubber oil pump belts, timing chains that are not fit for a bicycle, 20PSI of operating oil pressure starving the front bearing, poor surface finish, low tension piston rings, tiny piston oil drain holes, extremely poor metallurgy, excessive low RPM loading, plastic bearing coatings to compensate for poor lubrication and so much more.
For those who are younger, we really could use virgin quality cast iron with which to make a block, head, and crank and simply install quality parts. No need for cylinder liners, valve guides, valve seats or 'clearance adjustments' due to the high rate of Aluminum expansion. And it could be done with 'lightness' in mind. A well maintained engine could easily last forever, and be rebuilt multiple times.
Rubber oil pump belts, timing chains that are not fit for a bicycle, 20PSI of operating oil pressure starving the front bearing, poor surface finish, low tension piston rings, tiny piston oil drain holes, extremely poor metallurgy, excessive low RPM loading, plastic bearing coatings to compensate for poor lubrication and so much more.
For those who are younger, we really could use virgin quality cast iron with which to make a block, head, and crank and simply install quality parts. No need for cylinder liners, valve guides, valve seats or 'clearance adjustments' due to the high rate of Aluminum expansion. And it could be done with 'lightness' in mind. A well maintained engine could easily last forever, and be rebuilt multiple times.
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I don't think manufacturers have forgotten, they are more concerned with aiming for a price and durability point.
Price - as cheap as possible...save a penny an engine times 100,000+ engines
Durability - as long as it makes it out of warranty coverage
Even in the case of the GM debacle...my guess is they made plenty of $$$ over the years through cost cutting to cover this blip in their radar.
So true.
I remember going bonkers over my 1988 Toyota truck with the 4 cylinder 22R engine. They used nickel in the engine. Strong block. LOL. Plastic timing chain sprocket.
Head gasket went at 450k miles.
Loved my 2000 Silverado 4.8L push rod V8. Tranny went at 300k miles. It never consumed a drop of oil.
Most corporations will let the consumers suffer as long as the directors are "sure" it will save / make money or market share. A well crafted class action lawsuit might temporarily change their decision.
We all know that Nissan did no wrong with their CVT transmissions, they just extended warranties on SOME of them in SOME countries for... reasons? This story has been repeated many times.
Can someone show current up to date info where the recall says that engines in use checked out and not deemed to be damaged for an engine replacement will still be specified the original 0W-20 instead of the 0W-40 like the original recall info indicated? I don't think that happened. Instead, what happened is the new replacement engines coming out of the factory will still specify the 0W-20. But any engines on the road deemed not requiring a replacement engine will be speced to use 0W-40.
I just watched that video, and two of the 8 rods (both on the same crank journal) were totally smoked. All of the other 6 rods have very worn bearings ... way more worn than they should be at 50K-60K miles this engine supposedly had on it. He also said he thought the crank thrust bearings were excessively worn. I'm betting the reason the two rods on the same journal smoked themselves was because they wore more than the other 6, and at some point wore to the point where they quickly ate themselves up and it was all down hill from that point. Once journal bearing wear gets to a certain point, they can destroy themselves in a short time. Those rod big ends were super hot due to the bearings seizing up and spinning. If that continued, one of those rods could have locked up, snap and window the block.
So what caused all those rod bearings to wear that much in 50K-60K miles? If the oil viscosity to too low, it's going to cause the MOFT to go to zero and cause wear like that. As discussed in many journal bearing type threads, journal bearings do not like low RPM and high loads, something that could happen with a truck like this if doing some heavy towing, etc. Low speed and high loads can really reduce the MOFT in journal bearings. And that's a good reason to have higher oil viscosity for those kind of use conditions. My bet is those 6 rods that showed extremely worn rod bearings was due to lots of zero MOFT conditions. This is why GM specified 0W-40 for these engines still on the road. They can't spec 0W-40 for a new factory engine because it would get them into trouble with the EPA/CAFE regulations, as others have mentioned.
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Thank you for such an informative post. I've always been intersted in trying to understand how this stuff works. You mention had to start using "special design features" to be able to use oils lower than xW-20. We recetnly got the wife a Rav4 Hybrid and I'm pretty dumbstruck as to how 0w-16 is able to protect the ICE. I'm even more concerened because I plan on getting a '26 when they come out and am thinking they will likely be mandating a 0w-8. I thought Toyota was achieving this mainly by the extremely high molybdenum content of TGMO. I've since learned that the A25A family of engines use some interesting "features." The pistons have an alumite (anodized) surface coating on the upper compression ring lands. They also have diamond like coatings on the edges of the of the upper compression rings and on the oil control rings. The skirts also have a polymer/resin coating. The crankshaft bearings also have this polymer coating, and I assume likely the connecting rod bearings as well. I think it's neat that Toyota did that, but speaking for myself, it doesn't inspire a lot of confidence. If anything, it makes me think that Toyota perhaps couldn't get these engines to run reliably on these really thin oils without these mods.
I don't know. I may be wrong. It could just be that these were ways to further reduce friction in the engine to help them meet CAFE targets.
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Did they originally spec a 0w-8 or 16? Or are you speculating on them not going to thinner oil as they seem to have been with almost every new model year.
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Toyota might have been inclined to continue their trend towards thinner, ie 0W16.
But this is very high output from a 3 cylinder engine.
I am comparing this oil spec with Corolla, Camry, RAV4.
There are also coolant jackets between cylinders. Temperature control is a huge factor.
A driver would always want to do successive UOAs and see what their specific driving conditions lead to IMV.
These engines have ~ 42 % thermal efficiency and thin oils make for a good marriage.
Proper and effective AF/AW additives in the oil helps when the film thickness goes to zero and parts start rubbing on each other. But they can only help so much. The are obviously pretty important in the boundary lubrication realm, along with proper materials and the material hardness/wear resistance. If materials use for part that live in the boundary and heavy mixes lubrication realms aren't right, no oil will keep them from eventually wearing (ie, cam lobes or rings not properly heat treated and hardened). Preventing wear is mainly the job of the film thickness (keep the MOFT high enough to prevent rubbing), and the tribofilm from the AF/AW additives then takes over to mitigate wear after the film thickness goes to zero and rubbing starts. Film thickness from viscosity is key, and the AF/AW tribofilm is the secondary backup to preventing wear.
https://www.machinerylubrication.com/Read/30835/lubricant-film-strength
A lot of those special coatings are meant to give less friction and less wear when the oil film can't fully do its job from a low viscosity oil. Another thing they can do is make the journal bearings a bit wider so there is more load carrying area which helps keep the MOFT higher under more load (ie, force in the rod riding the bearing on the power stroke and under high HP output situations). But if you're not scared of going up a grade, it's not going to hurt anything and will give some added engine wear protection headroom. If I had a car that speced 0W-8, I'd be going with 0W-16 for sure, maybe even "go wild" with a 0W-20 even if it was still under warranty.
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If I end up getting that car, I will likely go really wild and use a 0w-30. I know in then past it's been advised that it's generally OK to go up a viscosity grade or two, but I don't feel like that applies anymore with these newer engines. Not when the manufacturer has owners manuals globally that spec going up as high as 3 or 4 viscosity grades.
I don't even have that car yet and I'm already researching 0w-30's lol.
On my wife's car I will likely go with a 0w-20. She is pretty easy on her cars, and hers being a PHEV, she drives in EV mode probably 90% of the time. I'm going to look for a 0w-20 that's on the thicker side of the spectrum though. Since the ICE in her car rarely comes on, I feel that might be better to help keep shear due to fuel dilution at bay.
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I was wondering about this myself. I was wondering if the original plan of switching to 0w-40 was an idea from the bean counter brigade in hopes of getting the engines to last past the warranty period. After that, too bad so sad for the owners. It wouldn't surprise me if someone from their legal department advised them that would be a terrible idea and the potential consequences from lawsuits would far outstrip any potential savings. Not to mention the potential loss of sales due to damage to reputation. This way, it looks like they are standing by their customers.
I watched the video OP posted and it was informative and I like that guy and tried to be very objective ...
However, it didn't change my mind that when in doubt, use a thicker oil. And since I am cautious:
Say Hello to My Little HT/HS Friend!
I mean a little bit of extra heat and mpg hit on the right side of the curve hasn't killed any engines! No?
But we can't say the same if you move too far to the left. Yes?
However, it didn't change my mind that when in doubt, use a thicker oil. And since I am cautious:
Say Hello to My Little HT/HS Friend!
I mean a little bit of extra heat and mpg hit on the right side of the curve hasn't killed any engines! No?
But we can't say the same if you move too far to the left. Yes?
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I'm betting some people with those engines in the recall range started running thicker oil shortly after the vehicle was new. It would be interesting to find some of those engines, tear them down and compare to the ones that failed with the 0W-20.
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