The dirty little secrets of Top 10 lists are in the methodology, as Forbes found out with its weirdly inaccurate "10 Dirtiest Cars" list. (It's the end of the year, so it's time for a lot of Top 10s.)

But we see no such problems in the EPA Green Vehicle Guide, which rates vehicles not only on tailpipe emissions but also their carbon-dioxide emissions.

CO2 ~ fuel usage

Fuel consumption is almost directly proportional to CO2 emissions, so it's not surprising that the best cars for the climate--ranked by their carbon dioxide output--turn out to be the highest-mileage models sold in the U.S.

The EPA ranks cars from 1 to 10 on two scales, one for tailpipe emissions and one for CO2. Ratings vary slightly by state, since California and 12 other states have tighter emissions standards than the rest.

2010 Honda Insight

2010 Honda Insight

2010 Ford Fusion Hybrid

2010 Ford Fusion Hybrid

Angular Rear Exterior View - 2010 Honda Civic Hybrid 4-door Sedan L4 CVT

Angular Rear Exterior View - 2010 Honda Civic Hybrid 4-door Sedan L4 CVT

SmartWay and Elite

Users can sort results by two levels: SmartWay, which requires at least 6 on each scale and a combined score of 13, or the harder-to-get SmartWay Elite, which requires 9 on each scale.

For the 2010 model year, in Ohio--which doesn't use California's standards--nine different models of five vehicles got both the highest score of 10 for CO2 emissions and the SmartWay Elite rating:

  • Toyota Prius (51 mpg city, 48 mpg highway)
  • Honda Insight (40 / 43) - four models
  • Ford Fusion Hybrid (41/36)
  • Honda Civic Hybrid (40 / 45) - two models
  • Mercury Milan Hybrid  (41/36)

In more stringent California, 12 vehicles achieved the same distinction for 2010. One Civic Hybrid and two of the four Insights fell off the list, but six more vehicles were added:

  • Ford Escape Hybrid (34 / 31)
  • Lexus HS250h (35 / 34)
  • Mazda Tribute Hybrid (34 / 31)
  • Mercury Mariner Hybrid (34 /31)
  • Nissan Altima Hybrid (35 / 33)
  • Toyota Camry Hybrid (33 / 34)

The different emissions levels can get arcane pretty quickly--do you know the difference between a SULEV and a PZEV?--but the basic rule applies: The higher the gas mileage, the better a new car is for the climate.

[EPA Green Vehicle Guide via USA Today]


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