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About the Ratings
Use the Glossary of Terms to explain terms and abbreviations used on the About the Ratings page.
The About the ratings page explains how the various ratings in the Guide are calculated and what they mean.
Overview
- This Guide gives environmental scores for cars and trucks based on emission levels and fuel economy values.
- The scores range from 0 to 10, where 10 is best.
- The scores can be used to compare all vehicles and all model years against one another.
- The best environmental performers receive the SmartWay designation, which means the vehicle scores well on both Air Pollution and Greenhouse Gas.
- EPA periodically evaluates the greenhouse gas and air pollution score criteria to ensure that they accurately reflect the state of the vehicle fleet, while enabling us to reserve SmartWay certification for the cleanest, most fuel efficient vehicles available. As a result, environmental scoring thresholds are subject to change. Please note that a vehicle's scores and SmartWay status reflect its environmental performance relative to other vehicles for model years with the same scoring thresholds only.
- EPA and the California Air Resources Board are working together so that that this rating system continues to be harmonized and effective nationwide.
Air Pollution Score
- This score reflects vehicle tailpipe emissions that contribute to local and regional air pollution, creating problems such as smog, haze, and health issues.
- Vehicles that score a 10 are the cleanest, meaning they emit none of these types of pollutants.
- Every vehicle listed in this Guide meets federal EPA or California emission requirements. Manufacturers may choose from a range of eligible emission standards for each vehicle; all the vehicles they sell in a model year must average a particular maximum emission requirement.
- Before a vehicle model can be sold, sample vehicles are tested under controlled conditions. Their tailpipe emissions are captured and measured with sophisticated monitoring techniques. Results of these tests determine the emission standard that the vehicle meets. All similar vehicles are required to have tailpipe emissions no higher than the standard.
- Emission standards are for the major pollutants in vehicle exhaust:
- NMOG, NMHC, or THC—types of carbon-containing compounds, including hydrocarbons
- NOx—Oxides of Nitrogen, which combine with hydrocarbons to create smog
- PM—Particulate Matter, tiny particles of solid matter that lodge in the lungs and deposit on buildings
- CO—Carbon Monoxide, a colorless, odorless, poisonous gas
- HCHO—Formaldehyde, a lung irritant and carcinogen
- This chart shows the Air Pollution Score for the most commonly-used EPA and California emission standards. To see the emissions levels associated with each standard, go to the table of vehicle emission standards (1 pg, 25k, About PDF) and Air Pollution Scores. For more details, go to the summary of current and historical emission standards (6 pp, 54k, About PDF).
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Fuel Economy
- The fuel economy values provide EPA miles per gallon (mpg), city and highway estimates for each car and light truck.
- These estimates are the same as those seen on the window stickers of new vehicles and in the Fuel Economy Guide published annually by EPA and DOE, available at auto dealers, public libraries, and online at www.fueleconomy.gov
- The Green Vehicle Guide has been updated to reflect the improved fuel economy procedures that EPA put into place beginning with model year 2008 vehicles. The new procedures give fuel economy values that more accurately represent real world conditions; for most vehicles, this means values that are several mpg lower than in the past. The Green Vehicle Guide has similarly adjusted the fuel economyvalues given for pre-model year 2008 vehicles, which will allow fuel economy comparisons between vehicles regardless of their model year. The original fuel economy estimates of pre-2008 models that were posted on the window stickers can still be viewed in the downloadable data files for each model year prior to 2008.
- Combined fuel economy is calculated from the City and Highway fuel economy values as follows:
Combined fuel economy = 1 / [(0.55/City fuel economy) + (0.45/Highway fuel economy)]
For example, if City = 20 mpg and Highway = 30 mpg, then
Combined example = 1 / [(0.55 /20) + (0.45/30)] = 23.5 mpg
- These estimates are meant to be used to compare the fuel economy of one vehicle to another. Your actual mileage will vary depending on how and where you drive, vehicle maintenance, and driving conditions.
- Vehicles with higher fuel economy save natural resources and create less carbon dioxide–a greenhouse gas–than vehicles with lower fuel economy. Every gallon of gasoline burned puts 20 pounds of carbon dioxide into the atmosphere and takes money out of your pocket.
- For more information about the fuel economy estimates, see www.fueleconomy.gov
Greenhouse Gas Score
- This score reflects emissions of carbon dioxide (CO2)and other greenhouse gases. Scientists say that increasing the concentration of greenhouse gases in the atmosphere will change the planet's climate.
- The Greenhouse Gas Score is based on the vehicle's fuel economy. Vehicles with higher fuel economy burn less fuel to travel the same distance. As less fuel is burned, less CO2 is emitted. Vehicles with higher fuel economy receive a higher Greenhouse Gas Score.
- The emissions of CO2 and the Greenhouse Gas Score vary by fuel type, since each fuel type contains a different amount of carbon.
- The Greenhouse Gas Score includes the three major greenhouse gases emitted by motor vehicles: carbon dioxide (CO2), nitrous oxide (N20) and methane (CH4), adjusted to reflect the relative global warming potential of each gas.
- The score reflects full fuel lifecycle estimates, considering all steps in the use of a fuel, from production and refining to distribution and final use; vehicle manufacture is excluded. For petroleum products, full fuel lifecycle greenhouse gas emissions include those created during extraction, refining, and distribution of the fuel. For renewable fuels, it reflects the emissions from farming and processing the feedstock; CO2 that is absorbed by the growth of the renewable feedstocks is also accounted for, resulting in improved Greenhouse Gas Scores for renewables. The scores are based on national average fuels and processing methods using the Department of Energy’s GREET model (version 1.7); these values will change in the future, particularly for renewables, to reflect developments in fuels.
- The Greenhouse Gas Score has also been adjusted to reflect the improved fuel economy measurement methods that EPA put into place beginning with model year 2008 vehicles.
- This chart shows the minimum fuel economy (combined city/highway fuel economy) for each fuel type at each Greenhouse Gas Score. The miles per gallon vary by fuel type because each fuel has a different carbon content per gallon. This means each fuel creates different levels of CO2 emissions per gallon.
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- More information on climate change can be found at www.epa.gov/climatechange.
SmartWay and SmartWay Elite
- The SmartWay designation is earned by those vehicles that score 6 or better on each of the Air Pollution and Greenhouse Gas Scores and achieve a combined score of at least 13 when added together. SmartWay vehicles are good environmental performers.
- Please see the requirements for SmartWay and SmartWay Elite gasoline, diesel, and E85 vehicles - Model Year 2008 & Earlier (1 pg, 370k, About PDF) and Model Year 2009 (1 pg, 388k, About PDF) for more details.
- SmartWay Elite is earned by those vehicles that score 9 or better on each of the Greenhouse Gas and Air Pollution Score. SmartWay Elite Vehicles are superior environmental performers.
- Now you can drive the SmartWay by saving yourself money on fuel and doing your part to help the environment.
- SmartWay is a registered service mark and cannot be used without the expressed written permission of the US Environmental Protection Agency.