Green Vehicle Guide

Greenhouse Gas Rating

This rating reflects vehicle tailpipe emissions of carbon dioxide (CO₂), the most prevalent greenhouse gas (GHG). CO₂ emissions typically constitute 99% of the tailpipe emissions of greenhouse gases.
Vehicles that score a 10 are the cleanest
Even though this rating only addresses what comes out of the tailpipe, it is important to note that the production of the fuel used to power your vehicle can also generate CO₂. For example, activities associated with fuel production such as extracting (or getting) the raw materials, transporting them to a processing plant, and converting them into motor fuel, as well as distributing that fuel, can all produce GHG emissions These emissions are not included in this rating.

Methodology for model year 2012 and earlier

For model year 2012 and earlier, EPA quantified greenhouse gases as CO₂e using emissions factors that were based on vehicle emission test results and fuel characteristics. Factoring in the global warming potential of each gas provides a vehicle's CO₂ equivalent (CO₂e) emissions. The CO₂e emission factors that were used:

Table 1: Tailpipe CO₂e Emissions Per Fuel Type
	CO₂		CH₄ and N₂O
Fuel Type	Pounds/Gallon	Grams/Gallon	Grams/Mile
Gasoline	19.59	8,887¹	1.9²
Diesel	22.44	10,180³	0.4⁴
E85	13.88	6,295⁵	4.0⁶
CNG	15.50	7,030⁷	6.8⁸

¹ Value is based on indolene fuel, a specific EPA test fuel.

² U.S. EPA, Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2007, Table A-90, EPA 430-R-09-004, April 15, 2009. Average value for Tier 2 passenger cars and light-duty trucks.

³ Value calculated based on 40 C.F.R. 600.113 carbon content.

⁴ U.S. EPA, Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2007, Table A-90, EPA 430-R-09-004, April 15, 2009. Average value for advanced diesel passenger cars and light-duty trucks.

⁵ Ethanol value is from the EPA's Final Mandatory Greenhouse Gas Reporting Rule for Petroleum Suppliers which uses the ethanol density value from the CRC: Handbook of Chemistry and Physics, 89th Edition, 2008-2009, Editor -in-Chief - David R. Lide; from Section 15: Density of Solvents as a function of temperature; and based the carbon share value on a calculation of the molecular weight of carbon in ethanol (C2H5OH) using the periodic table of elements. The table 1 value is comprised of 83% ethanol and 17% gasoline, accounts for 2% denaturant in ethanol.

⁶ GREET v1.8b available in RFS2 docket # EPA-HQ-OAR-2005-0161-0956 (spreadsheet "Vehicles").

⁷ GREET v1.8b available in RFS2 docket # EPA-HQ-OAR-2005-0161-0925.1 (spreadsheet "Emission Factors").

⁸ GREET v1.8b available in RFS2 docket # EPA-HQ-OAR-2005-0161-0956 (spreadsheet "Vehicles").