Gas mileage comparison between towing TT and 5'er?

I pulled a small 19 foot TT on a 2,000 mile trip with my old 2006 F-150. I got around 8 mpg. I pulled the same trailer about 800 miles with my 2010 Dodge diesel and got around 11 mpg. I now pull a full height stand-up bedroom 34 ft 5th wheel with my Dodge diesel and get anywhere from 9.5-11.5 mpg. Usually in the 11 mpg range. Doesn't seem to make much difference on the trailer size. I think the truck you are pulling with has as much to do with mileage as the trailer...

B.O.