I've been running my Saturno 500 on 98 octane, 95 at a pinch, but I wonder if that's really necessary, or if the 91 that's standard here in NZ would be fine?
When I had the engine apart I the combustion chamber and the piston crown didn't look to me like they'd demand high octane, and the CR isn't all that high. Moreover, Saturnos were originally designed/built for sale in Japan originally, and Japan had standardised on 91 Octane by then.
Is there any hard evidence that higher octane than 91 is necessary? Is anyone out there running their Saturno on 91?