Research results on Gas vs Diesel mpg costs...surprised!!

I doubt anybody uses a diesel for the mileage benefit. They use it for the towing ease, the exhaust brake and the whole improved towing ability that no gasser comes close to.
As far as a diesel costing more, I sold my last truck after ten years of use and got back every penny the diesel cost me in the first place. The truck was worth that much more because of the diesel.