[Capricio]

https://gmauthority.com/blog/2025/07...our-motor-oil/

I don't believe anything the General says anymore. From the comments section:

This is a perfect opportunity to remember that what’s good for GM isn’t necessarily good for you the consumer.

Let’s not forget that GM already specs the 0W40 for the LT1/LT2/LT4/LT5, which covers all the Gen V small blocks in performance vehicles (save the rather unique LT6). In fact they used to spec 5W30 for street and 5W50 for track, and updated new AND existing recommendations to 0W40 as it provides good protection for both. Note that all Gen V V8s have the same clearances, and in fact the heads, valvetrain, cam, and rotating assemblies of an LT1 and L86 have the EXACT same part numbers, the blocks are identical where it counts as well, just different castings for a few external bolt holes though they are still interchangeable.

0W20 and 0W40 have save viscosity when cold, so no increased wear on startup, but 0W40 will maintain higher shear strength and lubricity at high temperatures and loads vs 0W20, which is why they recommend it for sports cars that may see high rpms and track use. Heavier vehicles put more load on the engine, and especially when towing and hauling that will heat the oil just as much if not more.

They spec 0W20 because they can, and the lower viscosity under load makes just enough difference in fuel consumption and therefore emissions that they can add up over millions of vehicles to improve their CAFE and EPA fleet scores. Those same requirements prevent GM from permanently modifying the powertrain configuration in a way may alter those scores after-sale without a defensible reason. This is why disabling auto-stop/start and modes that disable AFM/DFM cannot be set permanently and must be changed every start-up, they have to default to the tested configuration.

GM knows that 0W40 is going to protect the engine more effectively, that’s why they recommend it as a Band-Aid fix to the L87s that MAY have defective finishing on the crank and/or rods, which is also a defensible reason as they can say it benefits the consumer by reducing the likelihood of failure. For engines that they have no reason to believe have the defects, however, they cannot defend recommending a different oil weight which is the ONLY reason they say to still use 0W20, as that’s the configuration the powertrain was certified with for EPA/CAFE standards.

Note that the difference in fuel consumption for oil weight, AFM/DFM, auto-stop/start and similar technologies is not going to make a noticeable difference on a single vehicle for most use cases. It’s only for the specific requirements of the respective test cycles, which may or may not be even remotely close to the way a given driver will use their vehicle, and only makes a difference when added up over millions of vehicles sold per year.

The ONLY theoretical advantage of 0W20 vs 0W40 other than cost/availability is the fact that it takes less friction modifiers and viscosity improvers to make a 0W oil behave like a 20W at temp vs a 40W, so less to break down over the oil’s life. This allows GM to get away with longer oil change intervals while still making it through the warranty period. But if you want your vehicle to last, this is basically GM admitting that you should use 0W40 and change your oil at regular intervals.

Do with that information what you like.

I guess we already knew our LT1s and LT2s have the EXACT same rotating assemblies/crankcases as he L87, the only difference is lower production numbers and the application, which shouldn't drive a different oil prescription, unless it's for policy compliance, not reliability.