Fuel, 4L60e and towing

[Joereese2]

Need some opinions, perhaps advice. I've got an 03 2wd Sierra that I swapped a 6.0 into and put a mild cam (towing) and had it professionally tuned at a local company that has a dyno, truck runs fantastic. So since I kept the 4L60e (it has the Sonax 2nd and 4th super hold servos and a huge cooler) ive generally kept it in 3rd towing because of my campers 6000lbs. I'm getting 8mpg and that's at 65 to 67mph at roughly 2850rpms. What are you guys getting with a 5.3 and 4l60 or a 6.0 with a 4l80??? Fyi my truck has 3.73s with 18 inch tires 

[Brian715]

Doesn't sound bad. Our work truck 2500 6.0 only gets like 11-12 empty....