04 6.0 before tune------avg 10.5 after tune guess what??? 10.5 shitty no matter what, and it doesnt matter what i tow it drops to 8.

 

I could see that with a 4L80, 2WD and 3.73's, Sure not a 4WD HD though!

 

I do not know about 4wd hd, but I have been pretty happy with our set up for this big of a engine. I am sure I could average 16+ mpg with our family of 6 and 70 lb lab in back on the open hwy not towing or dealing with mountain passes @ 70+ mph. I just seem to always be towing or going over passes around here!

 

10-12 around town in my 02 2500 AVY 8.1/4L80E 4x4 my commute is 95% highway (70-80mph)
I have gotten 13 a few times, but it was when I first got it. we did a tune with EFI Live and it kinda woke it up some (I dont think we tuned it as good as we could...some TQ management was left in I think since it had 125K on it and I really didnt want to hurt the trans) I also had a CPS go out (PITA btw) and at first it really never ran as good as it did before........maybe its in my head.

 

my 03 2500 avy with 8.1 4l80E 4X4 3.73gets best 10mpg worst towing 8000 lbs was 7.5
mpg. at the time it had SW long tube headers,3" true dual exhaust with 30" 3 chamber mufflers. vara ram cai, 2.5" lift 285/70R17 BFG KM2 mud tires.