So... between these two other threads you started:
https://www.tahoeyukonforum.com/threads/tahoe-6-2-with-10-speed-milage-issue-buyer-remorse.106573/
And
https://www.tahoeyukonforum.com/thr...mpgs-please-post-your-mpgs-to-compare.106583/
There are actually quite a few posts and responses from various owners experience with mileage based on different driving styles. Some various owners have given you feedback of their experience getting low 9-12 MPGs (that’s right in the range of what you’re experiencing). So If other owners are reporting how they experience MPG’s close to your range based on various driving styles how does any of that support “might be rare to have an mpg issue in something new” ?
This member goes on to talk about if they’re driving lots of short small trips then they see low MPG too.
You respond and say that is the type of driving you’re doing.
There’s been multiple posts in your other threads about new engine “break-in” from myself and other users. Giving advice and their experiences.
But to clarify a little further so that we’re all on the same page...
You purchase a brand new Tahoe RST with the 6.2L engine; 6.2 and 10 speed in the RST I believe is the “performance package”. A full size performance SUV with the largest engine option available. Yet your biggest most #1 concern that has you stressed out and worried that you got a “lemon” is the poor gas mileage you’re experiencing?
To be honest if the #1 concern and experience you care about is gas mileage then maybe you purchased the wrong type of vehicle.