Hey John,
Well these new diesels are not the diesels of old.

CO2 emissions are 25% less than a conventional gasoline powered engine. CO, HC and NOx emissions are less than previous 'OLD' Diesels. Diesel fuel has lower evaporative emissions than gasoline. Diesel fuel also requires less energy intensive refining than gasoline.

Diesel engines generally emit higher amounts of NOx and particles than equivalent gasoline powered cars, even though CO and HC emissions may be lower, and total emissions are lower due to much better fuel consumption. The current TDI Volkswagens typically emit slightly somewhat lower than the Tier 1 limits for NOx and particles (around 0.052 g/mi of particulate matter [PM] and 0.82 g/mi of NOx per EPA data), but the CO and HC emissions are far below the Tier 1 limits and well below the emissions of the equivalent gasoline engine.

Furthermore, most of the unregulated toxic gaseous emissions tend to be lower for diesel engines. For example, benzene (which is a known carcinogen) is lower in diesels by nearly an order of magnitude (i.e., factor of ten) than an equivalent gasoline engine. Diesels also tend to be significantly lower in emissions of alkenes (e.g., ethene), carbonyls (e.g., formaldehyde), and semivolatiles like polyaromatic hydrocarbons (PAHs, many of which are known or suspected carcinogens).

PM has always been regulated by mass (e.g., grams per mile). However, very recent studies show that particle number may be the more important aspect of PM emissions. According to a "real world vehicle testing report" by University of Minnesota renowned combustion particle scientists, new data show that PM number emissions from modern gasoline cars may equal or exceed diesel PM levels. It goes on to discuss gasoline PM emissions and that fact that gasoline engines may need a particulate filter much like that of a diesel. The University of Minnesota study showed that newer and older gasoline vehicles matched or exceeded diesel PM number emissions at high speed/load . It appears that diesel engines equipped with diesel particulate filters (DPFs), as many are now in Europe, will have a significant advantage in PM emissions over gasoline engines. Other recent studies are suggesting that gasoline PM is generally more toxic that diesel PM.

The emission levels from diesel engines tend to remain more-or-less constant throughout the useful life of the engine, whereas gasoline engines have many more emission-related components which deteriorate and lead to higher and higher emissions as the engine gets older.

Speaking of cancerous stuff..., we have/had MTBE in our gasoline here, that stuff scares the crap out of me.

I can say, my old gas car would give a nice plume of smoke from time to time as it burned oil, and not to mention dripping it out of the leaky seals. talk about environmentaly unfriendly. theres no way the tdi is producing more emissions than the car i gave up

now as for the diesel, i've yet to see smoke, i cant even smell the car running (you know that typical diesel smell) this car is much better than my old one when it comes to emissions. The VW TDI has the lowest emmissions ever of any diesel powered car. have to gimme credit for burning 1/2 the fuel as well.

i never said it was a simple choice, but i'm still happy with it