To my knowledge, the higher compression rate the engine has, the higher octane number is needed, and that's it. So if your S&S engine has a compression rate that demands 96, that is the minimum number you should you should use. If you fill up with anything higher, you are buying fuel with a property you do not need, so it is a waste og money IMO. I did try 98 octane fuel on my previous Lotus Elise S2, which is more of performance car/engine than a MW3, I'd say. I noted no difference at all.
