we have had a 1986 22 foot Chev RV with a 350 GM engine 3 speed automatic transmission fuel mileage averaged 9-11 MPG in hills and flat country

we now have a 26 foot Flair RV with a 454 G.m.Gas engine and overdrive automatic transmission Fuel injected unit in alberta flat lands we can get 11.7 to 12 MPG and in hill areas 9- 10 MPG But the 454 engine drives like a dream lots of power and cruise like a bus watch out on downhills as the unit will run away unless you select lower gears