I don't have any numbers to back this up, but... no you are not off the
mark thinking diesel emmissions are cleaner.  Yes they are smellier and
look dirtier, which turns many people off of diesels (I kind of like the
smell..), besides the "diesel clatter," and the larger exhaust particles
are supposedly carcinogeous (when breathed directly, say, camping out on
the roof of a semi for a year).  The big "but" is, that diesel engines put
less greenhouse gasses in our air, partly because they burn hotter, and
cleaner, and partly because they simply burn less.  Finally, with the new
TDI (which I have suggested before, would make the gasoline engine
obsolete if US industry would not block us from this wonderful technology)
has CO2 emmissions so low, they can't be counted.
Go for a TDI!

Mark
'85 retrowesty "Duckmobile" (in the hospital, getting its head checked)