Presently, most NASCAR cars use high-octane leaded fuel. However, because of the appeal made by the advocacy group Clean Air Watch to the Environmental Protection Agency (EPA), NASCAR is running a series of tests of alternative fuels, including unleaded types of gas. These have been found not to cause any engine problems, and starting with the 2008 season all NASCAR cars will be using a special unleaded fuel developed by the EPA and their new fuel supplier, Sunoco.