Indy says the C59CX plug was the best for both alcohol and gas. I also had thought that with alcohol a colder plug would be best and I think I may just try it and see this year.I will only be out a couple of $$$ to put a set in and make a pass to see which is best. I have been having to order the plugs from Indy,but was told @ Advance they could order the plugs for me. Unlike most I don't have a problem with Indy but Advance is only a couple of miles up the road and no min. or shipping charges.