The EPA started really tightening up diesel emissions in the late 90's. The big jumps came with particulate filters in 2007, and urea injection in 2010. Urea i

The EPA started really tightening up diesel emissions in the late 90's. The big jumps came with particulate filters in 2007, and urea injection in 2010. Urea injection by the way, is the technology that VW decided to cheat instead of use. The unique thing California has done is to require all vehicles be retrofitted with particulate filters.