Class A to a Fifth wheel......What to expect on MPG???

Well, we have officially started the hunt for the fiver and a truck. I am surprised by how much fifth wheel you get for the money compared to my class A. I was also surprised by how little they weighed. We looked at a 38' triple slide Blue Ridge that only weighed a hair over 12.5k dry. Going to do some serious looking this weekend and with any luck I will be able to sell my truck out right and not have to worry about trading.