It is disappointing to read about VW's admission to a deliberate engineering decision in circumventing a Federal clear air standard with their 'Clean Diesel' engines (irony, anyone?). Cheaters.
Whether EPA standards are too strict is completely beside the point, as VW knew the standards before choosing to certify their engine for this market. There is no question that CRs with DPFs are a vast improvement in an absolute sense, but again, beside the point, given the EPA standard. For years, I drove diesels for their combination of performance & fuel economy, not because I drive a lot. I owned an ALH TDI, but disliked the smoke it made. I sold my 2010 Golf earlier this year not wanting to be stuck with dealing with a failed HPFP or clogged DPF, and because I wanted AWD. I attribute both of these TDI engineering challenges in our market to the quality of US diesel fuel.
Two questions come to mind:
1. What attributes of U.S. #2 Diesel fuel (refining standard, compared to EU diesel), if any, caused VW to resort to devising this coping mechanism?
2. How did BMW & Mercedes deal with meeting compliance in their diesels?