This legislation mandates that the Administrator of the Environmental Protection Agency (EPA) revise existing regulations within 120 days of enactment. The revision will permit manufacturers to utilize a 31 percent lower gram per mile carbon dioxide (CO2) value for flexible fuel vehicles (FFVs) when determining fleet average CO2 standards. This specific reduction applies compared to the CO2 value of an identical vehicle make and model that is not an FFV, acknowledging the environmental benefits of E85 fuel. Congress finds that E85 fuel, made with corn starch ethanol, significantly reduces greenhouse gas emissions per mile traveled compared to gasoline, as indicated by the GREET model. Furthermore, the Administrator retains the authority to apply an even larger percentage reduction in the CO2 value for FFVs if supported by future updates to the GREET model developed by Argonne National Laboratory.