A Class C of the length you're considering will have a reduced payload compared to a shorter one say about 24 to 28 feet and a little less mileage due to the extra weight, especially in hilly country. We have a 23 ft Class C with the Ford V10 engine and get about 10 mpg, maybe a little less in hilly country, and then can get 11 mpg in flat country like the midwestern USA. We used to have a 30 ft. Class A with the Chevy 454 engine and it only got about 8 mpg on a good day; it was nice when you got to your destination, but we like our shorter Class C much better, especially when driving.