The soon-to-be-released 2007 Mercedes-Benz E 320 Bluetec is billed as the cleanest diesel ever, but it produces too many emissions to be sold in five states.

The sedan is the first of 10 models expected to use the Bluetec common-rail direct injection engine, and the vehicles include an aftertreatment process to reduce nitrogen oxide emissions. However, that still was not enough to meet the regulations of California, New York, Maine, Massachusetts and Vermont, according to Edmunds.