I just encountered a typical lay media puff piece about the 2009 diesel Jetta, which won the Green Car award this year.

Did you know that the next generation of diesel-powered cars and SUVs is 98 percent cleaner than diesels sold just two years ago?

No, but I also didn’t know that the older models were that dirty!

Did you know these new clean diesels offer 23 to 43 percent better fuel economy than the same vehicle with a gasoline engine?

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Sounds impressive! Until you go to the EPA green vehicle website and discover that the gasoline version with a standard transmission gets an air pollution score of 9 compared to this car’s 6.

This car does get a higher GHG score, but if you accept the findings of the Union of Concerned Scientists that a gallon of diesel creates 17 percent more GHG during the refining process, then the GHG score drops to 7, making this car no better than the $17,400 gasoline version in this category.

And finally, did you know this new generation of clean diesel-powered vehicles offers efficiency matching that of gas-electric hybrids?

Again, going to the EPA website and comparing this car to its closest competitor, the Prius, you find the Prius gets an estimated 65 percent better city mileage and 10 percent highway. How can you call that a match? Maybe they were referring to the Cadillac hybrid.

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To compare it to a Prius, which is a hatchback with automatic transmission, I would need to take the $1,600 wagon and the $1,100 dual clutch options, driving the price to around $24,700. It has been predicted multiple times on the blog that the introduction of low sulfur diesel would eventually allow somebody to market a diesel here that meets air pollution standards in all 50 states. It was also predicted that this car would be complex, expensive, and have the attendant engineering compromises:

That said, it’s clear the TDI was designed to perform at the pump, not on twisting back roads …

The car is rated to accept up to a 5 percent blend of biodiesel, but even if you have a source that uses waste, a 5 percent blend won’t overcome the 17 percent refining penalty. You would need to be willing to risk your warranty and go to a waste biodiesel blend higher than 17 percent to coax this car to be greener than its gasoline cousin. Don’t hold your breath for algae-based biodiesel. According to this recent relatively balanced article, it remains perpetually a mere five years from viability (h/t the inestimable Mr. Steenblik).

This is definitely a good-looking high-mileage car. Compared to most other cars on the road, it is a real winner. They just need to stop comparing these diesels to equivalent-sized electric hybrids. Diesel technology is tapped out with this car. The electric hybrid concept is just getting started.

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