6.8 V10 E450 mpg on Ford

Plan on 7-8 mpg when budgeting for a trip. Typical Class C's have a lot of aerodynamic drag and rolling resistance due to the overall weight. The drag builds up a lot as you go faster than 50mph. Tires should be inflated to proper pressures for your rig (not too soft). I have gotten as high as 9 mpg and as low as 7mpg depending on wind conditions, level terrain vs mountianous,and traffic conditions with slowing and accelerating.Cost of fuel in an RV is only a small part of the total cost of ownership and operation.