VW being dirty is a misleading argument. I used to have a VW diesel and was part of TDIclub. The california air resources board kept tightening the noose around anything internal combustion, despite stopping the leading cause of smog years ago. VOCs were the problem (unburned vapors from gasoline and light hydrocarbons), but CARB went overboard about NOx and particulates when it comes to diesels. Oddly enough, the gas direct injection engines make more particulates and have a harder time than diesels, but as a new technology were given less strict standards. Ask a BMW or VW gas direct injection owner about carboned up valves!
What VW did was what tuners did to increase economy. Advance timing and reduce intake clogging EGR rate. Mileage going up means less pollution in the long run.
But no, the US/CARB testing has nothing to do with real world fuel use. A 6000 lb SUV with a v8 that is set for low efficiency tuning is "less polluting" in their books than a 3000 lb car with a turbo gas or diesel inline 4. Meanwhile in euro standards, that v8 has a hard time passing. That's why we have hybrid SUVs here that get 18 mpg considered as great, while Europe has the same SUV with a smaller yet powerful diesel getting 25 mpg or gas getting 20 (ford started that with ecoboost though) that they cannot bring here!
Last joke about what VW did. Well, in the TDIclub we helped other diesels too, such as mercedes benz and BMW. Turns out they too have cheated in similar ways to pass CARB for the few diesels they bring here. The only difference is that VW is a big player in the USA compared to Benz/BMW.
Interesting, i always heared they tampered with it that when the car was in neutral and the wheel didn't turn it knew it was being tested and it went into a sort of passive mode. I also read that vw did extensive research in making the car less polluting. They came up with a real solution with an additive called
'urea' if i'm correct increasing the building costs of each car with 300 dollars and then this cheating software as a second option. Well, we all know how it went down from there... today there's only one brand that is performing within these emission values: vw... if u can do it, why not do it right from the first time!?
on the other hand it is idd ridiculous with these new petrol turboengines exceeding these values. Where is the logic in that?