And you wonder why there are so many regulations. It's because of these circumstances that the government has to SPELL EVERYTHING OUT, or business will act like little children and say, "well you didn't say take of my cloths before I get in the shower."
Since this is a technological site I think it's interesting to consider that VW (and all the others as we're now seeing) can't make a clean diesel.
Well, they CAN make a diesel run clean, but only under specific controlled conditions for a tailpipe sniffer test.
The logical conclusion is that when the diesel engine runs clean, it has other undesirable characteristics. This, because, if it COULD run clean AND also have desirable characteristics, they would have it run clean all the time. It's simpler. Why add complexity to the powertrain control modules to have two or more performance modes?
But they don't have it run clean all the time because they can't.
The only logical conclusion is that when it runs clean it has poor performance. No power. No torque. Something bad. Or, they run it so lean that the temps spike and it would hurt engine life. I don't know. They figured out some tricks to fool the sniffer and they couldn't live with it in that mode full time.
The automakers have reached the limits of technology in cleaning the diesel emissions, at least with the diesel fuel available in the USA.
We would be better off to have more diesel out there in passenger vehicles. It has great fuel efficiency, the engines last a long time, lots to like about diesel. I hope this fiasco doesn't kill it off.