OK THE “LAW” IS EMISSIONS.
The old TDI’s could not be sold new in New York State due to there exhaust emissions. You could buy a used one though no problem. There was never a law aginst diesel’s in New York, just a rule that a NEW CAR VW DEALER could not sell a new TDI’s (between 02-08) in the state.
If you notice VW call’s all the TDI’s “CLEAN DIESEL”. It’s because the emissions coming out of the tail pipe are cleaner then those coming out of a gas engine. They do this with a Particulate Filter that helps to clean the exhaust gas better, they also use a throttle body in the exhaust system to help “back pressure” the cat’s on cold start to get them up to operating temp faster.
All of the other Diesel’s for sale in the US outside of pick up trucks use a solution called “AD BLUE” this is really just re-invented animal piss that they found out when spraying it into the exhaust gas before it exits the tail pipe, it will help lower harmful emissions. A gallon will normally last about 8k miles and cars such as the VW Touareg, The Merceds Diesel, and the BMW Diesel x5 all use the same additive.
My Ford pickup has the same deal… can these be overridden like mine is so that it functions as an exhaust brake? would be badass on a small car IMO. I love it on the truck.