6.0 Chevy V8? Close to 10mpg. 7.4/454? Couple mpg less. Class A has a great view and usually good basement storage. Against that, parts availability, tricky subsystems like A/C, and near-zero crash safety. Class C doesn't ride quite as well, less view, less storage. But easier parts access, cheaper parts and tires, standard chassis systems like wiring and A/C. Most generous/flexible sleeping arrangements. We don't go far enough and stay long enough to justify additional investment and maintenance. Ours isn't luxury but it isn't punishing either. We've stayed in it two months on two occasions and one month on another.