http://www.greencarreports.com/news/1100225_why-did-volkswagen-cheat-on-diesel-emissions-in-its-tdi-cars
The problem is that U.S. and European emission standards for diesel diverged sharply in 2008. The U.S. adopted much stricter rules (known as "Tier 2, Bin 5") on emissions of virtually every component of diesel exhaust.
Europe, on the other hand, stayed with the so-called Euro 5 standards. Its emission limits only moved up to roughly the U.S. level this year.
But while other makers--including Toyota, Honda, General Motors, and Ford--began to introduce gasoline hybrid-electric vehicles to boost their fuel efficiency, VW chose to stick with diesels.
Also, keine Chance mehr für Diesel-Fahrzeuge demnächst, gut so.