Imagine getting a defective V8 replaced in a safety recall, only for its replacement to fail as well, which is exactly what happened to 26 vehicles fitted with GM’s 6.2-liter V8. GM also received another raft of complaints about engines that failed after getting the recall’s alternative oil-viscosity remedy, with the resulting investigation surging to almost one million vehicles.
Meanwhile, the 4.0-liter V8 in certain Mercedes-AMG vehicles has its own factory documents that reveal weaknesses. And even if this company’s issues are nowhere near as serious as GM’s, these weaknesses challenge the notion that V8s are always bulletproof.
GM’s 6.2L L87 V8
Still Under Investigation After A Massive Recall
GM’s naturally aspirated 6.2-liter V8 is one of its most important engine creations, code-named L87. It sits inside some of the brand’s most expensive vehicles, such as the Cadillac Escalade, where it produces 420 hp and 460 lb-ft of torque. Shoppers can also come across the L87 in a range of Chevrolet and GMC full-size truck and SUV families. So, when it developed some considerable problems, this was far more than just a niche performance engine issue.
In 2025, the trouble began in earnest, and earlier issues surrounding the L87 became impossible to ignore. Much of the current drama revolves around GM’s recall of just under 600,000 US market vehicles as part of NHTSA campaign 25V-274. This covered certain 2021 to 2024 Chevrolet Silverado 1500, Suburban, and Tahoe models, as well as the GMC Sierra 1500, Yukon, and Yukon XL.
The recall also pulled in some Cadillac Escalade and Escalade ESVs that had the L87 on board, built between March 2021 and June 2024. And by GM’s estimates, about 3% of the recall population actually contained the engine defect in question, which was just about as serious as any engine defect could be. According to information provided by GM, conrod or crankshaft components might contain manufacturing defects that could cause engine damage or even outright engine failure.
Exploring The Issue In More Detail
2021 Chevrolet Silverado Realtree 6.2 Logo L87Chevrolet
These engine issues came down to two principal causes, both linked to supplier manufacturing and quality problems: first, rod bearing damage due to sediment on connecting rods and inside crankshaft oil galleries, and second, a crankshaft issue where the dimensions or surface finishes were outside specifications. Either one of these conditions might contribute to bearing damage, which could lead to total engine failure.
Even worse, drivers might encounter this issue unexpectedly while the vehicle was moving, and the resulting loss of propulsion could lead to a crash. Otherwise, they could encounter knocking or banging, a check engine light, hesitation, abnormal shifting, high engine speeds, or a no start condition.
In its recall chronology, GM says that it identified 28,102 U.S. field complaints or incidents potentially related to the L87 crankshaft, connecting rod, or engine bearing failure. Of those recorded between April 2021 and February 2025, 14,332 included allegations of lost propulsion. Meanwhile, GM also identified 12 potentially related alleged crashes, 12 potentially related alleged injuries, and 42 potentially related fire allegations.
When a suspect vehicle arrived at a dealership, the fix depended on actual engine performance. Sometimes, technicians would replace or repair the engine, while those engines that passed inspection would receive higher-viscosity engine oil, as well as a new oil fill cap, oil filter, and owner’s manual insert. GM also initiated production improvements to the connecting rods and crankshafts to address any contamination and quality problems that it identified during investigation.
Sadly, for GM, that recall wasn’t the end of the story and the remedy itself became part of a subsequent investigation. This led to the NHTSA recall query RQ26001 in January 2026, which uncovered reports of engine failures after the recall work had supposedly been completed. The Office of Defects had accumulated 499 complaints by August 2026, alleging post-remedy engine failure among vehicles covered by the recall. Importantly, 473 of those vehicles had actually received the oil viscosity remedy and another 26 had received complete replacement engines. Separately, GM reported 6,953 complaints alleging post-remedy engine failure.
NHTSA Broadens The Investigation
2025 – 2026 Cadillac Escalade ESV 5th Gen (GM T1XX) Facelift SUVCadillac
Outside the recall population, matters went from bad to worse. NHTSA reported that it received 191 reports involving L87 engines produced after the end of the original suspect manufacturing window. This led to an escalation from the NHTSA, with the agency opening Engineering Analysis EA26005 in mid-August 2026 and expanding the scope to just under a million vehicles from the 2021 to 2026 model years. This investigation will look at both post-recall failures and engines that GM produced beyond the original recall period.
Of course, an investigation involving one million vehicles is not the same as an actual recall, like the original one that involved those ~600,000 vehicles, but the optics are not good. GM is dealing with an enormous volume of potentially related field complaints and incidents, safety recall reports of failure after both forms of recall remedy, and an expanded engineering analysis covering later vehicles. That is certainly not a good look for this 6.2-liter naturally aspirated V8 from one of America’s most famous engine families.
Mercedes-AMG’s M177/M178 V8
The Hand-Built Engine With Expensive Weak Points
While GM’s L87 engine issues may have started to take on nightmarish proportions, Mercedes-AMG doesn’t have quite so much on its plate. However, the company is still dealing with a factory paper trail covering its M177 and M178 units that makes the familiar image of a hand-built AMG V8 not quite so mechanically untouchable.
The 4.0-liter twin-turbo V8 in question is very sophisticated, even by modern performance car standards. Notably, its twin turbos fit in between the cylinder banks, in what Mercedes calls its “hot inside V”. These engines also have shorter exhaust paths to help with turbo response, and this allows the company to create a more compact engine package. Engineers then add direct injection and elaborate cooling systems to generate significant performance from those 4.0 liters, while the M178 variant, to be found in certain AMG GT applications, also has dry-sump lubrication.
Various M177 versions powered everything from the C63 and E63 to the G63 and AMG GT 4-Door. And Mercedes famously describes these engines as benefiting from its “one-man, one-engine” assembly philosophy. So, with such a pedigree, documented problems matter even more. This shines a spotlight on a recall in 2020, when Mercedes-Benz addressed 2,518 M177-equipped US vehicles. 20V-048 involved certain 2018 to 2019 E-Class, G-Class, S-Class, S-Class Coupe, and Convertible, as well as 2019 AMG GT four-door models.
Oil-Feed Issues Raise Serious Concerns
2016 Mercedes-Benz AMG GT Exterior Rendering Showcasing Engine Through Transparent HoodMercedes-Benz
The root of the issue appears to be that the material used in the oil feed line supplying the turbos did not meet production specifications. This could lead to thermal loading while driving, causing the oil feed line to leak with the potential for a fire, should the escaping oil reach hot components in the engine compartment. The fix here was to replace the turbocharger oil feed line.
The company’s own technical bulletin adds to the record with a 2019 entry describing M177 and M178-powered cars whose engines could intermittently lose boost while still storing a no-fault code. This may have been attributable to a problem with the pressure transducer or turbocharger vacuum supply. The same bulletin also talked about crankcase ventilation or purging that didn’t operate correctly, and the fix here was to replace purge lines or, on earlier cars, associated hardware.
Additional Oil-Related Concerns Complicate Matters Further
2018 Mercedes-AMG E63 S Wagon Front WheelMercedes-Benz
In July 2025, Mercedes issued another bulletin covering all M17X variants with complaints about oil leakage or an oil smell from around the rear of the engine and engine-to-transmission interface. Mercedes identified the rear main seal or possibly the rear main seal plate as the source of the leak. Crucially, Mercedes instructed its technicians to replace air/oil separators if they could confirm that oil was coming from the seal, before cleaning the area and testing it again. If the leak continued following their work, only then were they told to replace the rear main seal plate and seal themselves.
Those specific instructions matter because an oil separator is part of an engine’s crankcase management system. When such a system is not regulating crankcase conditions properly, this can lead to problems manifesting elsewhere, including at the seals. Mercedes’s own repair instructions link an oil leak complaint to the initial replacement of both separators, before the more invasive seal repair work is considered.
Mercedes-Benz
In a separate development, Mercedes extended the warranty on the engine thermostat found in certain M17X vehicles. The warranty covered 15 years/150,000 miles and was due to a thermostat sealing ring that could detach, delaying coolant warm-up and potentially illuminating the MIL.
Even though the AMG V8 is a sophisticated and extremely powerful engine family, it does have genuine, documented weaknesses linked to turbocharger oil supply, crankcase ventilation, oil separators, the rear main seal area, the thermostat, and boost control hardware. Still, none of those problems make the M177/M178 an inherently bad engine. While plenty of them may still accumulate substantial mileage without catastrophic internal failure, these special hand-built units are clearly not immune from expensive problems.
Sources: GM, Mercedes-AMG, NHTSA.
