Obviously true. Because even though the Ducati owner's manual clearly stated to use Hi Test fuel, it was making more HP on the mid grade.
There used to be a formula for compression ratio to octane rating, but I don't remember.
What was throwing me off, was the clatter, knocking, perceived ping, that I mistakenly attributed to engine noise.
To answer Stig's original question, I'm not new to scooters, Currently also own two Super 8 150's, the main reason I bought the Xtown. The 150's have a louder exhaust, and/or quieter CVT, because I've never heard noises like these coming from either of them?