NHTSA opens preliminary probe into more than 870,000 GM vehicles

[StephenPT]

Unfortunately the 6.2l is a perfect storm for self destruction. Since the 10 speeds have showed up the problem has been even more prevalent due to the Low RPM/High Torque loading on the 6.2l.

The 10L80 has been present in the GM Full-Size SUV platform since 2018. I could be wrong, but I don't remember hearing about any 6.2L's having bearing failure before the '21 SUV redesign. With the '21+ came the L87 and DFM and more than a handful of early life engine failures.

As has been mentioned before it's more likely an issue of being the perfect storm of DFM, 10L80 gearing, 0W20, DI, variable displacement oil pump, etc. etc.

 

[Jay P Wy]

The 10L80 has been present in the GM Full-Size SUV platform since 2018. I could be wrong, but I don't remember hearing about any 6.2L's having bearing failure before the '21 SUV redesign. With the '21+ came the L87 and DFM and more than a handful of early life engine failures.

As has been mentioned before it's more likely an issue of being the perfect storm of DFM, 10L80 gearing, 0W20, DI, variable displacement oil pump, etc. etc.

The L87 was used in the 2019 and newer Silverado & Sierra with the 10lL80. Are the 19 & 20s from the pickups having the same issues or is it 21 and newer? Did the 19 & 20 SUVs have the L86 or L87?

 

[StephenPT]

The L87 was used in the 2019 and newer Silverado & Sierra with the 10lL80. Are the 19 & 20s from the pickups having the same issues or is it 21 and newer? Did the 19 & 20 SUVs have the L86 or L87?

The NHTSA investigation applies to the following:



It's the L87 they are investigating - which as far as I know has only ever been coupled with the 10L80. In the '19-'20 SUVs it was the L86 with the 10L80 and those are not affected by the investigation nor do I believe anyone has ever had a pre-L87 experience low mileage bearing failure.

 

[jfoj]

Agreed!

Has anyone in this thread stated that the whole “warming the car up first is bad” thing is specifically a problem to the 6.2? (If so, I missed it.) Or, is this a “bad” practice for all gas engines? Because I’ve never heard such a thing before this thread — ever.

I’m not saying that it’s BS. I’m trying to learn and understand more about it. But yes, I’m skeptical about it.

The issue is not just a problem with the 6.2l, but more pronouced with all DI gasoline engines for a variety of reasons. Clearly warming up in the Winter is a bigger issue with fuel contamination than during the Summer, but allowing the engine to idle to warm up will allow more fuel to get into the crankcase regardless of the ambient temperature.

The 6.2l in the full size trucks and SUVs's appears to be configured to operated at Low RPM and under VERY High Torque loads on a consistent basis which puts tremendous pressure specifically on the rod bearings. The rod bearings are dead last in the oil flow path in these engines. Add to this LSPI which is aggrevated by fuel in the oil and the fact that the speced oil is probably borderline when fresh and likely inadequate once fuel is in the mix and the oil viscosity drops. Load the vehicles up and/or put a trailer on the back, things will not turn out well. Once fuel starts to dilute the oil, oil consumption typically increases, so the risk to the engine being run low on oil is much higher.

Fuel gets into the crankcase past the piston rings and moreso when the engine and engine oil is cold. Cold cylinder walls allow fuel to condense a liquid fuel really does not burn, this just adds to the visous circle of fuel dilution of the oil. The longer the engine takes to warm up, the longer you have conditions for excessive fuel to end up in the crankcase.

Still trying to gather data, but below is a graph of the engine oil temperature on the same 6.2l for the same basic time period. Starting ambient temperature is 5F different.

The blue curve is cold start and idling for 15 minutes.

The red curve is cold start with idling for 30 seconds then driving the vehicle for 15 minutes.

A few notes to consider:

1. The difference in ambient temperature between the 2 starts was 5F, so there is a slight offset in the curves.

2. The dip in the start of the graphs is the laten heat in the engine because the outside air temp was slightly lower.

3. When driving the oil temp started to increase at 93 seconds, when idling the oil temp started to increase at 151 seconds.

4. At the 7 minute mark when driving the engine oil was 104F, the idle oil temp corrected for the difference in initial temperature was 77F.

5. At the 15 minute mark when driving the engine oil was 171F, the idle oil temperature corrected for the difference in initial temperature was 125F

Even after a 15 minute drive the oil was not fully warmed up. So understand that shorter drives in the colder months will take more of a toll on the engine oil with fuel contamination.

 

[Jay P Wy]

The NHTSA investigation applies to the following:

View attachment 450592

It's the L87 they are investigating - which as far as I know has only ever been coupled with the 10L80. In the '19-'20 SUVs it was the L86 with the 10L80 and those are not affected by the investigation nor do I believe anyone has ever had a pre-L87 experience low mileage bearing failure.

Ok since the L86 is not affected and had the same trans and HP/TQ what changed between the L86 & L87? Seems to me as an engineer that's where the focus should be in looking for the problem.

 

[jfoj]

Ok since the L86 is not affected and had the same trans and HP/TQ what changed between the L86 & L87? Seems to me as an engineer that's where the focus should be in looking for the problem.

While the NTHSA is focused on the L87, there have been failures on the L86. Clearly complaints are being documented for the L87 failures, some multiple failures.

The primary change was from AFM to DFM and the compression ratio may have changed.

I have seen conflicting info on the compression ratio for the L86 engine, I have seen 11.0:1 on some GM documention and 11.5:1 on some other documents. But if the power/torque ratings are in fact the same then the compression ratios are likely the same.

The other thing that could have changed is how the transmission mapping and torque loading on the engine was programmed with the ECM/TCM/PCM.

GM clearly knows best what changed in these engines, vehicle configurations and tuning.

The L87 has documented "oversize lifter bores" problems and there have been some fairly accurrate reports of some problem bearings in 2021 that may have made it into some 2022 models. The problem is there are quite a few 2023/2024 failures noted and time will tell for the 2025 models.

 

[RG23RST]

Lifter bore issue was limited to 2023 units and even then not anywhere near all of them.

Purely anecdotal I see most 6.2 issues on refreshed MY22.5 and MY23 trucks. We don't do Cadillac stuff so it's rare to get a Tahoe in with that engine.

 

[StephenPT]

Here's the write-ups for the L86 and the L87. Reading up on the L86 it has the variable displacement oil pump, spec'd to use 0W-20, Direct Injection, etc. The one major change between L86 and L87 is the introduction of DFM...

https://gmauthority.com/blog/gm/gm-engines/l86/

https://gmauthority.com/blog/gm/gm-engines/l87/

 

[blanchard7684]

Here's the write-ups for the L86 and the L87. Reading up on the L86 it has the variable displacement oil pump, spec'd to use 0W-20, Direct Injection, etc. The one major change between L86 and L87 is the introduction of DFM...

https://gmauthority.com/blog/gm/gm-engines/l86/

https://gmauthority.com/blog/gm/gm-engines/l87/

Thanks...that is good info.

Same transmission. Same oil pump as before. Same oil. Same HP and torque (peak numbers anyways). Same rear gearing.

Only change was DFM. I'm sure there was other engine and transmission mapping changes to go along with this.

If DFM is activated is this putting additional load on the bearings? Be good to know how many bearing failures were on engines that had DFM disabled most or all of the time.

 

[Jay P Wy]

Thanks...that is good info.

Same transmission. Same oil pump as before. Same oil. Same HP and torque (peak numbers anyways). Same rear gearing.

Only change was DFM. I'm sure there was other engine and transmission mapping changes to go along with this.

If DFM is activated is this putting additional load on the bearings? Be good to know how many bearing failures were on engines that had DFM disabled most or all of the time.

DFM also puts a bigger demand on the oil pump (16 vs 8 shut off lifters). Maybe the low oil pressure to the mains at startup due to the added load on the oil pump has something to due with this. Odd thing is the 5.3l has the same DFM, so maybe it's the oil pump (variable vs non-variable).
Fords 6.7 diesel is known for killing main bearings over time because they are the last to get oil (valve train/cam are first). Also the 6.7l power stroke has a hollow cam which must be filled before the mains get much oil.