Which is the problem with euro deisels in the first place.
The Euro manufacturers ( I think Mercedes in particular) have been investing a lot more in "clean diesel" tech. My problem with it is that I really don't know that there is much net reduction (if any) in pollution (and that's real pollution, not stuff like CO2 being a "health hazard").
I have a "clean diesel" 2008 F250 with the diesel particulate filter. The 2007 F250s get on average 5MPG more than I do. Guys in states where it's allowed have removed the diesel particulate filter from their 2008s and have recovered their fuel mileage. Since everyone has to use the ultra low sulfur diesel now, all I'm doing is using more fuel to go the same distance as an older model diesel with only a very slight reduction in pollutants. The particulate filter uses fuel to burn particulates into fine ash - when it's working (about every other fill up) I can use the MPG lie-o-meter and watch my MPG steadily drop at a fast rate for the twenty or so minutes that it runs.
May European countries, Germany for instance, have a pretty Green culture, which is why they have always been using small diesels in small cars. Burning 20 gallons of diesel at 50MPG seems to me to be a better way to reduce pollution than burning 20 gallons of gasoline at 20MPG.