My SO found this. It shows what could be (can be?) done with the technology we have. Ford's thinking that the US will not buy a high mileage diesel car is a few years out of date ?
Buisnessweek
Buisnessweek
Ford's Fiesta ECOnetic gets an astonishing 65 mpg, but the carmaker can't afford to sell it in the U.S. ...
Ford's 2009 Fiesta ECOnetic goes on sale in November. But here's the catch: Despite the car's potential to transform Ford's image and help it compete with Toyota Motor (TM) and Honda Motor (HMC) in its home market, the company will sell the little fuel sipper only in Europe. "We know it's an awesome vehicle," says Ford America President Mark Fields. "But there are business reasons why we can't sell it in the U.S." The main one: The Fiesta ECOnetic runs on diesel.