GM Changes L87 V8 Oil Recommendation Again Amid Reported Engine Failures

General Motors changed the recommended oil viscosity for its L87 6.2-liter V8 again in 2026, marking the second oil-recommendation change for engines covered by the automaker’s recall. The latest change was reported as federal regulators widened their examination of the engine, although the specific new viscosity and GM’s technical rationale for changing it again have not been identified in the available public account.

The revision comes amid reported engine failures after vehicles received GM’s existing recall remedy and a newly expanded National Highway Traffic Safety Administration engineering analysis. That sequence raises a legitimate question about whether the remedy adequately controls the failure risk, but it does not establish that the earlier oil change caused any failure or that it failed to prevent every failure that otherwise would have occurred.

Why a second viscosity change matters

Oil viscosity affects several interacting functions inside an engine: how readily oil flows during startup, the film maintained between loaded surfaces, pumping losses, and behavior at operating temperature. A higher-viscosity oil can provide a thicker lubricating film under some conditions, but viscosity alone cannot correct every possible dimensional, surface-finish, contamination or component-damage problem.

That distinction is central to the L87 case. GM’s April 2025 recall cited manufacturing issues that included machining sediment in connecting rods and crankshaft oil galleries, rod-bearing damage, and crankshaft dimensions or surface finishes outside specification. Those are not interchangeable failure mechanisms, even if more than one can ultimately affect bearings or crankshaft operation.

The original recall procedure therefore separated engines into two groups. Dealers checked for diagnostic trouble code P0016 and replaced engines that failed the screening. Engines that passed received 0W-40 oil in place of 0W-20, along with a new filter, updated filler cap and revised documentation. GM also provided those inspected engines with special coverage lasting 10 years or 150,000 miles from their original in-service date.

Changing the recommendation again does not, by itself, prove that the first viscosity revision was ineffective. It does show that lubrication guidance for this recalled engine remains in motion. To assess the significance properly, owners and technicians need the exact new viscosity, the vehicles and production periods to which it applies, whether the change is mandatory or advisory, and GM’s stated engineering basis. Without those details, conclusions about the expected protection or tradeoffs would be premature.

Regulators are testing the remedy, not declaring a cause

NHTSA opened Engineering Analysis EA26005 on August 20, 2026, covering 997,743 Chevrolet, GMC and Cadillac trucks and SUVs from the 2021 through 2026 model years. The original U.S. recall covered 597,630 vehicles with L87 engines manufactured from March 1, 2021, through May 31, 2024. No broader recall has been ordered, and GM has not changed the existing recall population.

The agency is evaluating both the adequacy of the completed remedy and whether engines built after the original production window should be included. It has received 499 complaints alleging failures after recall work: 473 involving engines given the oil-based remedy and 26 involving replacement engines. NHTSA also received 191 reports involving later engines, while GM reported 6,953 post-remedy customer complaints.

Complaint totals are important signals, but they are not a final failure-rate calculation. They may require validation, can contain duplicate or incomplete accounts, and do not by themselves show whether each engine failed for the same reason. Investigators will need to connect service histories, build records, inspection results and physical failure evidence before determining whether the screening method, oil recommendation, replacement population or recall boundaries need revision.

The safety concern is nevertheless concrete. Reported symptoms include severe knocking, sudden power loss and complete shutdown while driving; the investigation file records at least one crash and one injury. NHTSA characterizes the potential consequence as “loss of motive power due to engine failure.” GM says it continues to cooperate with the evaluation and that customer safety and satisfaction remain priorities.

The decisive next information will be more specific than another complaint count: what viscosity GM now recommends, why it changed, and whether NHTSA concludes that code-based screening plus revised lubrication guidance provides an adequate remedy. Until that technical basis is public, the second recommendation change remains a consequential development but not a completed diagnosis.

By Thomas Caldwell — AMI’s senior editor for mechanical and mobility engineering, covering vehicle electronics, systems integration, electrification, chassis systems, propulsion, and safety policy.