11 plus or minus towing a 10k plus fiver. I live out west with lots of mountains and I'm not generally a slow driver, but also not really fast.
Not towing I average a little over 17 in my normal city/suburban commuting. Freeway runs at 80 average 18-19, and highway runs at 65 are around 21-22. Best 400 mile trip was over 23 which was summer, under 65 but quite a few mountains. Worst was a New Years freeway run at 80+ with temps between -8 to -12 at about 13 mpg.
Overall I love the truck and couldn't be more satisfied with it.