Data on Cars used for Testing Fuel Economy

The test data used to determine fuel economy estimates is derived from vehicle testing done at EPA's National Vehicle and Fuel Emissions Laboratory in Ann Arbor, Michigan, and by vehicle manufacturers who submit their own test data to EPA.

Each year, EPA provides fuel economy data to the Department of Energy (DOE), the Department of Transportation (DOT) and the Internal Revenue Service (IRS) so that they can administer their fuel economy-related programs.

• DOE publishes fuel economy label values in the annual Fuel Economy Guide.
• DOT receives the manufacturers' fleet average fuel economy from EPA, and determines if manufacturers are complying with the federal corporate average fuel economy (CAFE) standards.
• EPA provides IRS with the fuel economy data for vehicles which may be subject to the Gas Guzzler tax penalty. IRS is responsible for collecting those taxes from manufacturers. 

EPA requires auto manufacturers to change or update their MPG (miles per gallon) values on fuel economy labels (window stickers) if information comes to light that show that the values are too high. See revisions to fuel economy label estimates.