Burch, as your engine breaks in, your mpg's should increase a little more.
Our magic mileage number seemed to be about 20,000 miles on our diesel engine (we have 41,000 now) when I noticed an increase in mpg. We are getting about 6.8-7.0 mpg weighing 55,500 lbs. which I think is not too bad.
Like with any coach, hills and stop and go traffic kill our 'good' average. On long straight interstates, I can inch our mpg's up to 7.5 as we turn about 1,100-1,200 rpm's in six gear going 55-60 miles per hour.
Happy Camping,
MM.