Except where otherwise noted, the efficiency and emissions data we report in our vehicle comparisons come from the U.S. Environmental Protection Agency (EPA). Here is the original data published by the EPA (in Adobe Acrobat PDF Format):

EPA 2002 Model Year Passenger Vehicle Data

The data reported here falls into the following categories:

• Overall score, as determined using the method described in this chart from the EPA.
• Fuel efficiency
• Smog-forming emissions, consisting of the vehicles emissions of nitrogen oxides (NOx), hydrocarbons (HC), particulate matter (PM) and carbon monoxide (CO). Vehicles are scored on a scale of 0 to 10, based on the total emissions of these compounds. The scoring system is as follows:

  10: 0 - 1.0 lbs / 15k miles
  9: 2.8 - 4.1 lbs / 15k miles
  8: 5.3 - 6.3 lbs / 15k miles
  7: 7.9 - 11.8 lbs / 15k miles
  6: 12.3 - 12.9 lbs / 15k miles
  5: 15.1 - 19.8 lbs / 15k miles
  4: 20.8 - 25.0 lbs / 15k miles
  3: 27.4 - 36.3 lbs / 15k miles
  2: 39.0 - 40.6 lbs / 15k miles
  1: 43.7 - 58.8 lbs / 15k miles
  0: 63.8 - 121.1 lbs / 15k miles

• Greenhouse gas emissions, expressed in terms of CO2 equivalents. These include the three major greenhouse gasses emitted by motor vehicles: carbon dioxide, nitrous oxide and methane. These estimates include the full fuel-cycle including production, refining, distribution and final use. These estimates are taken from the U.S. department of energy's GREET model version 1.5, developed by Argonne National Laboratory.