I got 15.0 mpg on a round trip of 340 miles towing the TM this week between Ruckersville, VA. and Hanover PA.....a combination of highway and city driving. I got 15.3 mpg with the TM of mountainous interstate between Harrisonburg, VA. and the New York border last fall. Most of the time I get between 14 and 15 mpg with city/highway towing, unless there is a lot of mountain travel, which can dip it below 14 mpg.
I try to be a real conservative driver. I do maintain the speed limit, but might take a minute of so to get up to that on takeoff. I stay off the brake as much as possible with plenty of following distances. There are probably a lot of people behind me that don't like it, but they don't have to pay for my gas.
Chap