If you are talking vans, that is one thing. Straight trucks, don't even consider it. I personally have never had one since expediting, but one guy in our group had a gasser and 4-5 MPG was all he ever got. And the biggest problem was he only had a 50 gallon fuel tank. So he was fueling alot. I just can not imagine trying it in a gas engined straight truck. Back when I was working at the job I retired from, we had gas burners for years. The maintenance was like 3000 miles on them. I would not like that.