I am a member of a collegiate racing team where we design and build a formula style race car. Our power plant for our car is a Honda 600 F4i, that's why I'm posting this question here. Our problems began when during testing our clutch began slipping quite a bit under moderate throttle. We pulled the engine and went to change out the clutch pack, expecting to have to replace a toasted clutch. To our surprise the plates looked fine, minimal wear, only one plate showed even the slightest sign of overheating/discoloring. This raised a question, what was causing our slippage? At the time of the testing we were using Castrol Syntec 10w-40 which we've run for a couple of years without any issue. It seems a little unlikely but could the frictionless modifiers have been our issue? Our intake is restricted to a 10mm opening, so our little F4i is only cranking out 80hp. Which leads to part two of my question. After speaking to a Castrol rep we switched our oil to Rotella 5w-40 but I'm not convinced this is the best choice for our car. It spends most of it's races in the upper range of the rpm somewhere between 9k and 12k and isn't exactly the typical "motorcycle" application that this engine was designed for. In addition to a dry sump our car is also outfitted with an oil cooler, even with that we've seen some very high oil temps, (220+), but that's not typical. I just want to hear your guys' opinions on what kind of oil would be best suited for our application. Any information would be great, thanks!