This is in fact a serious issue. The Ford Focus is not the only example. My business associates who travel in Europe a great deal tell me that there are a number of international manufacture cars that get upwards of fifty (in some cases sixty or seventy) MPG on the road in Europe that cannot be purchased in the US at all.
With all due respect to John, not because the oil companies are making gasoline they want to sell at exhorbitent prices but because the fuzzys who make the rules at EPA don't like the smell of diesel fuel; think that diesels are noisy and do not like to hear them; and who observe old technology diesels and see the emmission as an undiserable side consequence. These fuzzys make the rules for all of us who would prefer to use diesel.
EPA: Bingo! Think particulates.
Got bit bad on one of two GM diesels in the early 80's, but I'd try it again, especially on truck or SUV or large car. Fuel economy makes a much larger diff there.
I thought people were starting to like the rattle of the big diesel pickups.