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I would certainly get a chuckle out of that, lol
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Video - Engineering Explained, Do Thin Oils Destroy Engines?
- Thread starter martinq
- Start date
A typical GDI engine (certainly a Hyundai / Kia ) has chewed up a 20 weight oil plus shearing losses by 4,000 - 5,000 miles (probably sooner) , so always error with a 30 weight oil . When it shears down - I still have a 20 weight oil instead of a 16 weight oil . If I were to use a 20 weight oil it would be M1 0W20 ESP which appears to be Mobil’s best 20 weight oil .
That's exactly where I'm at with my gdi 2012 Hyundai. Already replaced the engine recently, apparently wasn't rod issues, was the camshaft or crank, I forgot which. I'm going to stick with pup, the manual calls for 5w20 or 5w30; and I sorta hear pup can shear slightly faster than others. So I'll try 30 weight, hope for the best. I've been doing my darnest research for my best oil options, very difficult to chose. Either way, hopefully 30 weight will last, albeit hotter engine.
If that is really your concern, why wouldn’t you use a -40 grade?
I'm not terribly knowledgeable with all this. But my manual says no 40 weight for the 2.4gdi. heaviest is 30 is my main reason. It kinda gets hot where I'm at, is a thought of mine using pup, so just hoping the best. I used 5w20 all its life and still blew up, with this new engine I'll try 30, I would use 40 if manual said it's ok. I'm not to savy with this. Also, going to try to use top tier gas
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It really says that a 40-grade is not permitted? Top Tier gas isn't going to be an issue here.
I highly doubt it. Hyundai did the same thing as Chevy did and upped the oil spec to 5W-40 on all their turbo motors back in 2015ish.
for 2013 to 2017 turbo cars. I would extend this to today's Hyundai/Kia's if they are in rough service. Oh that's right.........Hyundai/Kia ONLY makes engines that have to be placed into "rough service category" the minute they are driven off the lot, because of metallurgy and design choice. I bet I am on borrowed time on my Hyundai, trashing the heck out of it daily. 17 psi to 23 psi boost. This includes a lived through LSPI event when brand new. She gets stressed. I just changed out the dual clutch at 60,000 miles with an OEM clutch pressure plate and dual mass flywheel that all were cryoed. No high perf aftermarket dual clutch exist to date.
If I remember correctly Hyundai/KIa took out the 5w-40 spec in the manual in 2015-16 as an approved oil for turbo motors, YET wanted you to use it up to 2017 turbos here in the TSB.
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The Tundra turbocharged engine failures continue. We all know debris was blamed, yet there is little evidence for this. Not to mention, cleaning manufacturing swarf became priority number 1 right away, yet the failures mount. It looks like the bearing part numbers have changed. Still some failures on 2025 models.
I asked Grok3 to calculate the failure rate based on miles, year and number of claims. It seems like the problem continues on at the same rate with even the newest variants, perfectly clean inside and new bearing part numbers. In all years, the new, low mile vehicles have just a few failures, with the majority under the bell curve centered around 30K miles. Hovering unchanged around 0.4% failure rate.
What also seems interesting is that the failure rate decrease a bit as the miles increase.
I asked Grok3 to calculate the failure rate based on miles, year and number of claims. It seems like the problem continues on at the same rate with even the newest variants, perfectly clean inside and new bearing part numbers. In all years, the new, low mile vehicles have just a few failures, with the majority under the bell curve centered around 30K miles. Hovering unchanged around 0.4% failure rate.
What also seems interesting is that the failure rate decrease a bit as the miles increase.
Interesting, then, that GMs first suggested "fix" was...a thicker oil.
I mean, we all knew it wouldn't work, and I think GM even backed off of it already, but if thin oil wasn't the problem, why would thick oil be the fix?
To me it makes sense to go up one viscosity. It gives you more protection in less stable operating conditions. This is a well done film which will not change those with those who will fall o n their sords for the sake of .5 mpg gasoline increase.
Hi DB: We have a CX-30 so I followed your older posts. I remember you said the OE ATF looked very good when you changed it and you would go longer next time which is exactly what I found when I changed ours at 37K. I’ll probably go 50K on the current fill. Did you run the oil 30K changing the Microgreen oil filter every 10K? I ask because I have a few Microgreens for my Ford Duratec (Mazda MZR design) engine….trying to decide how to use them. What filter and OCI are you running now and what is the miles on your Mazda now?
As far as the OP topic…I’ve often thrown in a quart or quart and a half of 5W30 (same brand) in my summer OCI. I do it mostly because I have it but I also feel the slight increase in viscosity won’t hurt anything and may even help with wear.
Unless something has changed in the GM recall, my take was that all engines under the recall that don't show any signs of needing a new engine will be specified to use 0W-40. The new replacement engines coming out of the factory will supposedly still specify 0W-20. This may be driven by CAFE regulations since GM certified those engines on 0W-20 for fuel economy, so they must stick with it or re-certify them with a different viscosity to see how it would impact the avg fuel mileage on the fleet for CAFE purposes.
https://www.consumerreports.org/car...d-due-to-potential-engine-failure-a5860939820
"Dealerships will inspect the engine and, as necessary, repair or replace it. They will add higher-viscosity oil to the SUVs that pass inspection, install a new oil fill cap, replace the oil filter, and update the owner's manual. Changes to the connecting rods and crankshaft were made and introduced into production by June 1, 2024."
Maybe the changes they made to the bottom end will tolerate 0W-20 better ... or maybe not. Only time will tell, maybe they will end up specifying 5W-30 down the road.
So this GM Authority article references EE's video, and the article did pick-up on that fact that more viscosity shifts the operating conditions to the right on the Stribeck Curve like I showed in post 39. EE seems to tow the line to use what's "recommended" in the OM. He might get some sponsors a bit nervous if he focused on how thicker oil can add engine protection, so he just brushes the subject matter.
https://gmauthority.com/blog/2025/0...-explains-differences-between-oil-viscosities
"GM’s goal in using a thicker oil in the L87 engine is an effort to increase the Hersey number so the engine spends more time in the hydrodynamic lubrication phase of the Stribeck curve."
"Fenske further explains why GM is making the switch from 0W-20 to 0W-40. Generally speaking, it’s inadvisable to increase the first number or decrease the second number in an engine oil’s viscosity, because it introduces the engine to a viscosity it isn’t designed for. However, increasing the second number isn’t as risky since the whole operating range of 0W-40 oil is within the operating range of 0W-20 oil."
Engines are designed to run a whole range of viscosity, and they must therefore be able to run the thinnest oil specified. OMs in other countries for the same engines show that's true (many examples shown in this forum), because if engines were that sensitive to viscosity no OM would show a range of acceptable viscosity anywhere in the world. The clincher is the engine must be designed to properly be protected in all driving conditions with the thinnest oil specified. If they can't do that, then there could be issues down the road like seen in these GM engines, and also seen in some Hyundai/KIA engines (they also went up in viscosity). As mentioned, Ford also went up a grade on the Coyote 5.0L V8 (not driven by any recall like these GM engines), and it wasn't for CAFE appeasement, it was for more engine protection.
https://gmauthority.com/blog/2025/0...-explains-differences-between-oil-viscosities
"GM’s goal in using a thicker oil in the L87 engine is an effort to increase the Hersey number so the engine spends more time in the hydrodynamic lubrication phase of the Stribeck curve."
"Fenske further explains why GM is making the switch from 0W-20 to 0W-40. Generally speaking, it’s inadvisable to increase the first number or decrease the second number in an engine oil’s viscosity, because it introduces the engine to a viscosity it isn’t designed for. However, increasing the second number isn’t as risky since the whole operating range of 0W-40 oil is within the operating range of 0W-20 oil."
Engines are designed to run a whole range of viscosity, and they must therefore be able to run the thinnest oil specified. OMs in other countries for the same engines show that's true (many examples shown in this forum), because if engines were that sensitive to viscosity no OM would show a range of acceptable viscosity anywhere in the world. The clincher is the engine must be designed to properly be protected in all driving conditions with the thinnest oil specified. If they can't do that, then there could be issues down the road like seen in these GM engines, and also seen in some Hyundai/KIA engines (they also went up in viscosity). As mentioned, Ford also went up a grade on the Coyote 5.0L V8 (not driven by any recall like these GM engines), and it wasn't for CAFE appeasement, it was for more engine protection.
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That sounds a lot more like a band-aid on a glaring design flaw/oversight than anything else.
have a look at i do cars channel on youtube, he did a 1.6 cr diesel that is specced an xW-20 in the US but the design historically started with xW-40. The conrod bearings showew wear on the top shell. That wasn't what condemned the engine, but to me it seems BMEP was a bit much for whatever oil was used in that engine.
Yes they are trying to shove their problem into the customer's lap! The resolution to this kind of problem is a good class action suit.
They are on their 3rd revision of the bulletin. The first (or second, cant rememeber which) revision mentioned the 0W-40 thing, and the revision after that no longer mentions it. Unclear if they meant the next revision to override the one that specified 0W-40, or in addition to...all they refer to is the make/model/year and "list of VINs within IVH" (their tracking system, it seems)
I believe they backed off the 0W-40 thing as a fix, realizing it wont really fix bad machining and/or out-of-spec parts.
Eric (I Do Cars on YouTube) did a second 6.2 tear down last weekend of an actual recalled engine. It showed the crankshaft hitting the block because of excessive end play. More interesting is that the thrust bearing doesn't look worn, though he couldn't verify (did not know the factory thickness spec). I don't think thicker oil would fix that, and I think GM agrees now too. It's just going to take a lot of money and a lot of time to produce and replace all the engines.
but is there truth to the claim that the cars that spec 0W-40 (like Corvettes) don't suffer failure using the same components?
I believe speccing a thicker oil invalidated the cafe credits, can't have a car tested on 0W-8 and systematically filled with 0W-40 and that would happen across a lot of brands if GM got away with this.
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