This bill makes it easier for people to convert their vehicles to run on alternative fuels like ethanol, biodiesel, natural gas, and hydrogen, while reducing environmental regulations on these fuels. The main changes are: First, it allows aftermarket conversions of cars to alternative fuels without being considered illegal tampering, as long as the conversion is well-engineered and doesn't make the car pollute more than before. Second, it prevents the EPA from regulating biomass-based fuels like biodiesel. Third, it creates new definitions for alternative fuel vehicles and gives manufacturers a significant boost if they produce enough alternative fuel vehicles—specifically, it adds 8 miles per gallon to their fuel economy calculations and automatically exempts them from EPA greenhouse gas regulations if they meet 2020 fuel economy standards.

In practical terms, this helps car owners who want to modify their vehicles to use cheaper or cleaner fuels, and it gives manufacturers financial incentives to produce more alternative fuel vehicles. However, the bill's most generous provision is the automatic exemption from EPA emissions rules for manufacturers producing at least 50 percent alternative fuel vehicles—meaning these companies could potentially avoid stricter pollution standards that other manufacturers must follow. The bill essentially trades stricter environmental oversight for increased fuel choice and alternative fuel adoption.