Hard to believe someone can get 17 mpg towing a TT like that.  We usually get 8-9 mpg with a V10 F250 with 4.1 gears and 29' TT.  It is what it is and I don't worry about it anymore.
The cost of gas has skyrocketed here lately and is now over $7 US a gallon.  Not good for RV-ers...  :(  They are blaming it on a production shortage but why does it always go up every year in time for the better weather, pffft.  We do all our RV-ing in the US so they're not accessing any of our cash.  :)  Now, if the exchange rate could only return to around par.