After reading these posts I am a little disappointed in my AT4. Just purchased it and love it except for the mpg. First tank (from the dealer who knows what they put in it) got 11.1 mpg. That was mostly city driving but I did buy it about 50 miles from home so the first trip was on an interstate and only saw about 17 mpg at best.
I filled up with the second tank and I am seeing over 12 mpg but it is only 87 octane and only have less than a hundred in it.
I am hoping on three things that higher octane will yield higher mpg, a cover will help and that the break in period will also increase the mpg.
I thought i did enough research but didn't realize that the mpg numbers were based on 93 octane. If I would have known that I would have waited until a diesel was available because the difference between diesel and 93 octane is negligible where I am.
I am blown away that with the AT4 lift causes so much loss of mpg vs a Denali. (But they look so much better)