Just found this thread after researching a very similar issue on my '21 Sierra 6.2L.
33k miles. Mostly serviced by a dealer I've trusted for 15 years. No issues until last two oil changes (first was the dealer, second was a third party). At around 15% life remaining, "oil low" warning goes on. Both times needed 2 quarts to get to proper level. No oil leaks anywhere to be found (undercarriage, driveway, garage, etc.). Theorized that they put in 6 quarts instead of 8 thinking it was a 5.3L. But two different places (in different states for what its worth)? At the dealer now for another oil change and they are going to track oil consumption as several others have stated here.
If any original posters see this, would love feedback on how your trucks are doing since.
