VW subverted US fuel regulations which are notoriously tweaked _against_ diesel. The NOx emission control would relax at _highway speeds_, not in the city. This

VW subverted US fuel regulations which are notoriously tweaked _against_ diesel. The NOx emission control would relax at _highway speeds_, not in the city. This was an engineer's response to a protectionist legal framework. Keep in mind that diesel engines are notably more power efficient than gasoline ones, ho knows how much less CO2 would have been emitted had diesel been allowed to become more mainstream in the US?