If you will believe a long-time engine engineer, I will tell you that Ethanol does not degrade the 3-way catalyst any more than gasoline or any other hydrocarbon fuel. Ethanol blends have caused some troubles with certain rubber/plastic components in the fuel systems of cars not designed to be ethanol tolerant.Odd, my spyder has the original main cat still at 166,000 miles using 10% ethanol from the local Shell station. Knock on wood, it is still working properly. When it fails it will get replaced with another cat. IMHO every little bit helps in reducing pollution so I will do my little part.