If you’re getting 7.5 then you’re doing good. There’s not really much you can do that will improve upon that. The big aerodynamically challenged, heavy as heck RV prevents any real fuel efficiency. Keep the speed down, light foot on the pedal, try NOT using cruise. Cruise is designed to keep your speed as set, regardless of fuel usage. Keep your tire pressures placard numbers. Lower pressures for a better ride may reduce mileage, but not significantly I suppose.
Some owners will invest in a Banks power pack, or a 5 Star tune. I know no facts as to how much they help.