This is certainly very impressive. Excellent MPG for such a large vehicle.
I do think GM of that vintage provides the best balance of power and value to cost if you look at it this way..
I agree on the value, you do need to look for a well-cared for version as there are so many out there and prices are all over the place.
As far as my MPG's, I meant to edit but timed out earlier....that's with premium fuel (93), and I'm driving as gentle as possible. Highway mileage is road trip highway, fill up before you hit the road, and fill up along the way. But I agree, 19-20 MPG for a 3 ton vehicle on a trip with no large elevation changes is pretty good.
Otherwise if I drive it like a sedan, I will get 14-15 city, and 18-19 highway...baby it and you can net an additional 1-2.
I have used 87 a few times, and it just doesn't feel as peppy, and I lose about 1-2 MPG. The L94 6.2 has slightly high compression for most modern street engines @ 10.5:1 so while 87 works, you should use 93 or maybe 89. The torque delivery is much improved with the 93.
Keep in mind, the 2nd row is either bench or captain's chairs, the bench DOES NOT RECLINE backwards, and can be a deal breaker on long trips, GM really screwed up here. The captain's chairs do recline however. We have the 2nd row bench and it works for us, the benefits of having the extra seat outweigh an occasional long trip, but they are still comfortable in the fixed position.
This generation of SWB models like the Tahoe and Yukon, don't have comfortable 3rd row seats for anything more than a small child, but is rather wide being a full-size SUV, the seat portion is almost on the floor, not terrible, but for long trips it would not be as comfortable. Your knees are higher than what would be deemed an ideal seating position.
The Suburban and Yukon XL have a raised rear floor under the seat giving a slight depression in the floor for your feet, much more comfortable for adults.
I'd you have young kids and won't tow anything over 3k, the Odyssey Touring or Sienna are exceptional family haulers....we LOVED our Sienna. The Yukon just fits our lifestyle better now, and I would do it all over again even with the 6-8 MPG hit over the V6 vans.