The Fueleconomy.gov mobile website allows users to estimate their car’s fuel mileage per gallon and other information related to their vehicle’s fuel usage. according to the Mobile Gov blog. The mobile website is maintained by the U.S. Department of Energy and is accessible on any phone that has web browser functionality. According to DOE, the mobile website users can calculate gas mileage (MPG), annual fuel costs, annual petroleum use, and the carbon footprint information for your car or truck. You can find more mobile products like the Fueleconomy.gov mobile website on the USA.gov Apps Gallery.