That coach is also on the front end of the 2009/2010 emissions systems that Cummins started using. You may want to see what sort of maintenance, if any, was done to the DOC/DPF system. We have a 400/450 Cummins, but my guess is that Cummins used the same DOC/DPF system on all of their OTR engines??
You may also want to have it plugged into the Cummins computers and see what codes may be sitting in the computer and make sure that the injectors are holding up. Bad injectors lead to major dollar problems with the DOC/DPF.
Otherwise, as I was told when I wanted to purchase one of these, if you are worried about the cost of fuel to get from point A to point B, these are not the motorhomes for you!!