Court Nixes Appeal Over Added Ethanol in Gasoline The Supreme Court has rejected challenges to Environmental Protection Agency decisions allowing an increase in ethanol content in gasoline. The justices on Monday left in place a federal appeals court ruling that dismissed challenges by trade associations - representing the oil industry, food producers, restaurants and others - to EPA decisions allowing a gasoline blend of up to 15 percent ethanol. The national gasoline supply is largely a blend with 10 percent ethanol.