The Flex Fuel Fairness Act of 2023 would require the Environmental Protection Agency to adjust how it calculates carbon dioxide emissions for vehicles that can run on E85 ethanol fuel blends. Under the bill, manufacturers would be allowed to claim that flexible fuel vehicles produce 31 percent lower emissions than comparable gasoline-only vehicles when calculating their fleet average emissions standards, based on research showing that E85 fuel reduces greenhouse gas emissions by that amount. The EPA would have 120 days after the bill's enactment to implement this change through regulation, and could potentially increase the emissions reduction credit if future research warrants it. The legislation would benefit vehicle manufacturers and ethanol producers by making it easier for automakers to meet federal fuel economy and emissions standards. There is no specific funding amount mentioned in the bill, as it primarily directs the EPA to revise existing regulations rather than appropriate new money.