Dirty driving: Top 10 worst polluters

A new version of Volkswagen's Touareg is among a group of next-generation diesel vehicles from Audi (owned by Volkswagen), BMW, Mercedes-Benz and others. These new and improved diesels will include special catalytic converters and a system that injects urea into the exhaust stream to neutralize pollutants and drastically reduce emissions.

They will start hitting the market late this year and are expected to receive an EPA air pollution score of 6. That’s enough to pass California’s stricter emissions standards, which so far have kept diesel vehicles from being sold there and in other so-called “green" states that have adopted California’s emissions laws: Connecticut, Maine, Maryland, Massachusetts, New Jersey, New York, Oregon, Pennsylvania, Rhode Island, Vermont and Washington.

The easiest way to minimize your carbon footprint with your next car purchase is to choose a model with the best fuel economy possible. But you don’t necessarily have to choose the most frugal car on the lot to do your part for the environment.

Experts say that realizing even minor improvements in fuel economy among the worst polluters on the road is the most efficient way to reduce greenhouse gas emissions overall. For example, choosing a base GMC Yukon with a 5.3-liter V8, which gets 16 mpg overall, instead of the high-end Denali version and its 14-mpg 6.2-liter V8 would save more than 130 gallons of gasoline per year for the typical driver, and eliminate 1.7 tons of carbon dioxide emissions, says Therese Langer, transportation program director for the American Council for an Energy-Efficient Economy.

“By comparison, achieving the same savings through improvements to a 42-mpg Honda Civic Hybrid would require a 25-mpg boost, to 67 mpg,” Langer says.

The EPA currently provides consumers with air pollution scores, fuel-economy estimates and greenhouse-gas-emission ratings for all passenger cars and light-duty trucks at www.fueleconomy.gov and www.epa.gov/greenvehicles.

A few states have enacted regulations that will require automakers to post labels on vehicles detailing the amount of greenhouse gases each one emits, along with how that model compares to the average of all cars and trucks from its model year. California and Connecticut will begin requiring such labels beginning with 2009 models, and New York will follow suit for 2010 vehicles.

Europe is ahead of the U.S. in requiring that such information be readily accessible to consumers. “In Europe, vehicle specifications now regularly list a model’s CO2 emissions,” says Francois Gravigny, an advisor for market research firm R.L. Polk and Company in Southfield, Mich. “Everybody in Europe knows what their vehicles’ CO2 emissions are.”

Although American consumers are becoming more aware of environmental issues, they’re a long way from choosing vehicles for purely altruistic ecological reasons. “By and large most people believe that they have a right, a God-given American right, to drive whatever car they want and can afford,” says Dr. Charles Kenny, a psychologist and president of The Right Brain People, a psychology research firm based in Cordova, Tenn. “Americans still have a love affair with their vehicles, which are associated in their minds with freedom and independence.

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