I had a chance over the weekend to take the coach out on an overnight trip to Cameron, Texas. The good news is that replacing my air filter and using a target speed of 65 mph yielded an increase in fuel economy to 7 mpg from 4.5 mpg. That is a huge improvement and probably paid for the filter on the first trip. Total round trip was roughly 270 miles and I put 38.13 gallons of diesel in. The method used was to top it off before leaving and then return to the same station to top it off again when I returned. The calculation is approximate because I forgot to document the mileage before leaving.
I also discovered that something is wrong with the shore power connection. When I connected it to the power it tripped the breaker and I heard a buzz from inside the bus. I suspect that something is trying to charge the battery bank in the bus and pulling too much current. I was using a 30A to 50A adapter as the location I was at only had 30A power. I opened the grey transfer switch box and observed significant fucker clustery (worse than cluster fuckery). It appears to be an electromechanical 3 way transfer switch. The coach can be powered by shore power, genset, and inverter/battery bank.
I did not have time to analyze the configuration in the field and will need to spend some time trying to figure out what is going on and how it is configured. Then I can figure out how it should be configured. One thing I did not like for sure was the electrical gear adjacent to the batteries with no venting.