this is the explanation?..
Our list of the year's 12 Meanest Vehicles for the Environment has traditionally been dominated by large SUVs and pickups with 8 or more cylinders per engine and four-wheel drive. After all, moving more metal (or moving it faster) means burning more fuel, which therefore causes more pollution unless extra steps are taken to control it. Model year 2007, however, sees an interesting development in the introduction of a number of diesel-powered SUVs and crossovers that meet some of the dirtiest standards still allowable in the country. Although these engines offer an efficiency improvement over comparable gasoline models, the poor tailpipe emissions performance of the diesel models is sufficiently damaging to the environment that it earns them a place on the year's Meanest Vehicles list. This year, nearly half of the list is populated by these diesel models, including the 3.0-liter diesel Jeep Grand Cherokee; Mercedes-Benz GL320 CDI, ML320 CDI, and R320 CDI; and the year's meanest vehicle for the environment, Volkswagen's 5.0-liter diesel Touareg.
Curiously, the manufacturers of these diesel models have already unveiled plans to bring cleaner diesel models to the country in 2008 containing more sophisticated emissions control systems that purportedly will meet the Tier 2 bin 5 emission standard. Mercedes-Benz, in fact, already has a diesel model on the market meeting the Tier 2 bin 8 standard, which is about two-thirds cleaner than the Tier 2 bin 10 standard to which the models on this list are certified. While reasoning behind DaimlerChrysler's decision to unveil a dirty diesel model for 2007 remains unclear, it is likely these models will only temporarily be on the market in this configuration.


