If you are concerned about finding diesel I would recommend Streets and Trips from Microsoft, which you can load on to your computer, than down load the mega-file from Discovery owners, which lists many diesel locations. For us the design of the front cap seems to one of the most important factors in determining fuel economy pulling a 5th wheel, we had a 32' Sunnybrook before our Montana which is much longer and weighs more but my mileage remains somewhere between 10-12. I average slightly over 11.5 on an 15,000 mile trip last year.
