Those pollution scores don't include greenhouse gas emissions (related to fuel economy) which are listed separately. Also the EPA pollution scale is based on the typical gasoline exhaust profile which makes it difficult for any diesel except the new generation of clean diesels to score high. For example, an older diesel may do pretty well on HC and CO emissions and keep up with the best of gassers, but because of higher PM and NOx emissions it gets knocked down to the bottom of the scale. You could say the scale is a bit biased.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL