Thanks guys, I suspected that was about right. It is surprising that the EVIC is so inaccurate. I was an airline pilot for many years, and the technology has existed to accurately measure fuel flow for decades. I don't get that. If planes were this aqccurate they would regularly fall out fo the sky with the pilot thinking they still had 3,000 lbs left.
I want to get rid of my 20" rims for some stock 17" with 265 75 17" rubber. I hope the thinner tire width will help fuel econ a bit. I'm not too fussed as fuel is pretty cheap but I feel bad buring so much of it.
Seems odd though that with all the technology in this rig, the fuel economy is so poor. I had a 5.7 Vortec 2000 Chevy Silverado with 33" BFGs, 4wd, extra cab, loaded with toys and accessories, roof rack, winch, etc. and it got 13 mpg pretty consistently around town and as much as 19 on the highway if I kept it to 60 mph.