I agree that net pollutant measuring is a good idea, but I don't agree that it should be accounted by gross volume. Passenger mile (or cargo tonnage per mile) would be a more practical consideration if you're truly serious about environmental impact.

I suspect that a reasonably tuned WBX vanagon carrying seven people would probably come in somewhere in the same "pollution per passenger mile" performance envelope  as a TDI sedan carrying a single occupant.

Happy trails,

Greg Potts
Toronto Ontario, Canada
www.pottsfamily.ca
www.busesofthecorn.ca
1973 Westfakia, 1987 and 1988 Wolfsburg Vanagons, 1991 Jetta

On 2012-01-21, at 11:11 AM, Dave Mcneely <mcneely4@COX.NET> wrote:

> I agree that hybrids will be the way to go.  I drive one because of the fuel savings and cleanliness.   But, diesel fuel can be cleaned so that it is quite good.  Considering the difference in fuel use of these small diesel engines versus gasoline, how do the emissions actually compare?  I have never understood why tailpipe emission is measured as it is, pollution as a fraction of the exhaust gas, anyway.  That means that spewing mega quantities of pollutant is ok so long as the engine is big enough.  If your vehicle is spewing out 0.2 units per liter, while mine is issuing 0.1 units per liter, but yours puts out 1 liter for every 3 of mine, then yours is cleaner,despite the greater fractional contribution.  If measured on the basis of pollutants per mile driven, rather than as a fraction of exhaust gas, then we might get somewhere.
>