Yeah, other people have chimed in on this issue, so I won't beat a dead horse, but there is clearly a demand for diesel vehicles, especially as the new turbo diesels have been able to be so effective on the fuel economy return. My dad's old gasoline 38' motorhome got about 7 MPG and then he bought a heavier 40' version of the same motorhome but just with a diesel pusher, got him up into the 9 MPG range. That was not enough to offest the cost of the fuel, but they did have to stop less and the diesel engine takes a LOT less fuel when idling.
Gasoline engines burn fuel at roughly the same fuel to air mixture all the time, not quite but pretty close. Diesel engines are variable so at idle they can burn like 100:1 and when at full throttle more like 8:1 or whatever.