I don't know if anybody takes the time to read previous posts but I find information in this thread quite confusing?
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I use exclusively 91 RON in the last 30 years and on previous occasion 91 or 95 RON.
I have never, repeat never, had a plug fouling, starting, carbon build up or any other fuel related problem, while using this grade of fuel.
Those that promote the use of higher RON fuels (including AvGas, WTF!!!!!) in such engines are, without so much as a sceric of credibility.
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I have no experince and only anecdotal knowledge of using ULP in LyCons, Jab engines. My local flying school is exclusively Jab aircraft, they all run on ULP 98 RON, have done for very many years, apparently without any negative effects. My Rotax powered aircraft has a preference for 98 RON - will run on 95 RON and if needs be AvGas .
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Perhaps I'm being a little picky but if you were trying to learn something by following this thread I doubt you'd have much success.