GM Owners Want Thicker Oil In The Next-Gen V8: Here's Why

For more than a decade, General Motors has leaned heavily into efficiency-focused engine technologies across its V8 lineup. Starting with the 2014 model year, cylinder deactivation features and ultra-lightweight oils like 0W-20 became standard. On paper, this approach worked well. Power output increased and fuel economy improved. However, at the same time, owners' and enthusiasts' confidence was fading in the long term reliability of these engines.

That concern came to a head with the 6.2 liter L87 V8. Nearly 600,000 trucks and SUVs from the 2021 through 2024 model years were recalled after GM identified connecting rod failures linked to lubrication issues. The thinner oil was unable to keep its strength when dealing with high loads and temperatures. The result, according to critics and lawsuits, was metal-to-metal contact that led to catastrophic engine failure.

GM's response has been telling. For recalled engines that pass inspection, the fix is not a redesigned bearing or revised oiling system, but thicker 0W-40 oil and a new oil filter. That change alone has fueled debate, as many GM V8 owners no longer believe thin oil is worth the risk.

Polling conducted by GM Authority asked readers what they thought would be the type of oil used in future GM models. The results show that a strong majority of readers pointed towards the brand using heavier oil in its next generation small block V8s. The current oil being used, 0W-20, was given minimal support. The majority of polled readers backed 0W-40 or even a return to 5W-30, which was used in older trucks until 2013.

Some have perceived the engineering choices centered around thinner oil as being driven not by real world use, but by test cycle efficiency. Full-size trucks are frequently used for towing and extended highway driving, which are conditions that place higher demands on engine lubrication. For years, enthusiasts were told modern engines were designed specifically around low viscosity oil. Now, in the wake of widespread failures, GM itself is mandating thicker oil as a corrective measure. At the same time, some owners are suing GM, claiming the switch to 0W-40 increases fuel consumption and lowers vehicle value. The debate has effectively flipped.

The oil strategy that GM developed was built around pressure from regulations like the Corporate Average Fuel Economy standards. Models could derive small but meaningful improvements to efficiency by using low viscosity oil, which is why many modern engines use them in the first place. However, recent changes to federal fuel economy rules have reduced that pressure. Without the threat of penalties hanging over them, manufacturers can now afford to prioritize durability, especially with lower fleet targets and rescinded incentives for tech like stop-start.

Sales data complicates the narrative. Despite reliability concerns, Silverado and Sierra sales increased significantly after the 2014 introduction of these new V8 technologies and remained strong through the adoption of additional technologies like Dynamic Fuel Management. Performance improved, fuel economy rose, and buyers kept showing up. Looking ahead to GM's Gen 6 small-block V8s (which it spent almost a billion dollars on) expected to debut in the 2027 Silverado and Sierra, the oil question has become symbolic. It represents a broader choice between chasing incremental efficiency or restoring confidence in long-term engine durability, and owners have made their preference clear.