General Motors is changing the oil in hundreds of thousands of recalled V8 trucks and SUVs and calling it a remedy. The automaker has issued updated service bulletins telling dealers to use Mobil 1 FS 0W-40 oil in 6.2-liter L87 engines that passed inspection but were not replaced under a sweeping 2025 recall. That recall covers roughly 600,000 U.S. vehicles from the 2021 through 2024 model years, including the Chevrolet Silverado, GMC Sierra, and Cadillac Escalade. Previously, dealers were instructed to use Mobil 1 Supercar 0W-40. The reason is not performance.

It is cost and supply. Supercar 0W-40 is more expensive and harder to source. FS 0W-40 is cheaper, more widely available, and still meets GM's dexosR high-load specification. On paper, both oils share the same 0W-40 viscosity rating. In practice, they differ in chemistry and intended application.

FS offers broader use and slightly more wear protection. But the real issue is not which premium oil is poured into the crankcase. The recall itself stems from a supplier-related defect involving rod bearing contamination and crankshafts potentially out of specification. Engines that fail inspection are replaced. Engines that pass get new oil and go back on the road.

That approach is now under scrutiny. More than 1,000 complaints alleging continued engine failures -- including failures in replacement engines -- have triggered a federal investigation by the National Highway Traffic Safety Administration. Multiple lawsuits, now consolidated into a class action, argue that switching oil viscosity does nothing to fix mechanical flaws that can lead to sudden engine failure. Some replacement engines have reportedly suffered from failed lifters and damaged connecting rods.