Fuel cost becomes significant for full timing, towing 10k-30k miles per year. For weekender RVers at 2-3k miles per year? Not so much.
Gas towing high walled RV gets 8-10mpg.
3/4-1 ton diesel pickups get 12mpg towing the same RV.
A mid-sized diesel SUV (Jeep Grand Cherokee, VW Touareg, BMW X5, Audi Q7, MB GL) will get closer to 15mpg towing, but their limits are lower like in the 6k loaded RV range and they cost a bit more than mainstream competitors that do not offer diesels and again are stuck at 8-10mpg towing.
Air streams tend to require about 15% less fuel than a conventional RV.
In summary, you have to spend more (on the TV, on an Air stream, etc) to save.
Buy used - saves the most.
