I am new to the forum and FMCA as I had just joined a year ago when I purchased my first coach. Fuel economy was mention early on in the discussion so I thought I would add my two cents worth.
I have a 2008 Itasca Meridian with the ISC 350 Cummins engine. I have found that if I am pushing it (70+) my fuel economy goes way down (7 mpg). If I keep it between 55 and 65 I am getting over 9 or 10 mpg.
Just food for thought.