The popular YouTube channel Engineering Explained, known for breaking down complex automotive engineering topics, has tackled one of the biggest automotive recalls in recent memory: the General Motors recall of nearly 600,000 vehicles equipped with the 6.2L V8 L87 engine. Hosted by mechanical engineer Jason Fenske, the video walks through the root of the engine failure issue and explains GM’s unusual recommendation to switch from 0W-20 to 0W-40 oil in these vehicles.
At the center of the recall is a manufacturing flaw. According to GM and covered extensively in Fenske’s video, some engines may suffer from sediment left in the connecting rods and crankshaft oil galleries during production. This debris, along with improper crankshaft specs and surface finish, can cause rod-bearing damage. The outcome? Potential engine propulsion loss, sometimes severe enough to require a complete engine replacement.
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Why Is GM Recommending a Switch to Thicker Oil?
Following inspection, GM is directing dealers to replace the original 0W-20 oil with high-viscosity 0W-40 Mobil 1 Supercar oil in affected vehicles. But why would a simple oil change be the answer to a manufacturing problem?
Fenske, leveraging his engineering background, explains that the change in viscosity is intended to help the engine operate under more favorable lubrication conditions. The secret lies in an often-overlooked engineering principle: the Stribeck curve.
The Stribeck Curve: A Key to Understanding Lubrication
The Stribeck curve is a graph that shows how friction behaves under various lubrication regimes. On this curve:
- The Y-axis represents the coefficient of friction.
- The X-axis represents the Hersey number, a formula combining oil viscosity, sliding speed, and load pressure.
This curve has three distinct regions:
- Boundary lubrication: Direct metal-to-metal contact; high friction.
- Mixed lubrication: Partial separation between surfaces.
- Hydrodynamic lubrication: Full oil film separates moving parts; lowest friction.
GM’s strategy aims to increase the Hersey number by using a thicker oil, which shifts the engine’s operating conditions into the hydrodynamic lubrication region—where friction is reduced and metal parts are better protected from wear.
What Is the Hersey Number and Why Does It Matter?
The Hersey number plays a crucial role in determining where on the Stribeck curve an engine operates. It’s calculated using this formula:
Hersey Number = (Viscosity × Speed) / Load
By increasing viscosity—from 0W-20 to 0W-40—GM raises the Hersey number, making it more likely that the engine will maintain hydrodynamic lubrication and avoid harmful metal-to-metal contact.
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Is It Safe to Use 0W-40 in an Engine Designed for 0W-20?
Fenske addresses this concern directly. Normally, it’s not advisable to change oil viscosity beyond the manufacturer’s recommendation, particularly increasing the first number (which affects cold-start performance) or decreasing the second (which affects high-temp protection). But in this case, the entire operating range of 0W-40 fits within the engine’s tolerances.
That means the switch to thicker oil isn’t likely to harm the engine—and could very well prevent the damage GM is trying to mitigate.
Final Thoughts: Should You Be Concerned?
If you own a Chevy Silverado, GMC Sierra, or another vehicle with the 6.2L L87 engine, this recall and oil change recommendation are worth your attention. Engineering Explained’s breakdown helps demystify what could otherwise be a frustrating and technical service bulletin.
The key takeaway: The thicker 0W-40 oil is meant to safeguard your engine by enhancing lubrication under stress. While it won’t solve the underlying manufacturing issue, it’s a proactive measure to reduce risk and extend engine life.