Keep the coach exterior as clean as possible. Wash it on a regular basis and and use the expensive wax for fiberglass. The slicker the surface the less drag it has.
Use the lightest engine oil recommended by the manufacturer. Heavy oil creates a tremendous drag on engine rotation. The oil pump creates drag (power loss) on the engine. Heavy oil makes the loss of power much greater for no real reason so match your oil to for engine and driving conditions.
Change your spark plug wires. Some vehicles have a problem with spark plug wire deterioration. Change them when you change spark plugs.
Consider a less restrictive air cleaner. You can find these at speed shops in your area.
Change your fuel filters. A new fuel filter can increase your mileage by one to two more miles per gallon of fuel.
Check the exhaust system. Make sure that the exhaust system is not restricted by a plugged catalytic converter or a damaged exhaust pipe.
Check your tire pressure. Ignoring the importance of proper tire pressure will insure a waste of fuel. Low tire air pressure will add a drag to the vehicle that can increase fuel requirements.
Refuel before your empty. Make plans to refuel the vehicle no later than 1/3 of a tank. Running the fuel tank any lower can cause sludge and debris at the bottom of the tank to enter the pick up tube and create potential blockage.
Store diesel motorhomes full of fuel. Diesel model RV's should be stored with the fuel tank full to reduce the build up of condensation sludge within the fuel. Water in fuel can damage the system and should be quickly evacuated. Remove water from fuel using the Drain Filter located on certain model RVs, or by having the system serviced by a qualified technician.
Get a tune-up. Its good to get minor tune-ups, where you check your the vehicles belts and hoses, every 30,000 miles and a major tune-up every 60,000 miles. Poorly maintained engine components require excess fuel supply. Follow the manufacturer recommendations for regular inspection of engine hoses and filters, and by performing routine oil changes. During engine maintenance procedures check fuel lines for signs of leaks that may be unknowingly draining the fuel supply.