You have to remember, epotech lives in England. 50MPG over there is commonplace. They're smart enough there to have high compression, quiet running, extremely efficient diesel engines over there.
I still have no idea why people here in the states still have this stigma attached to diesel and don't want anything to do with it. It's a better fuel, running in better engines, and can blow the doors off anything gasoline for MPG. If MPG is your goal, small, direct-injected diesels are the way to go.