aiseh not this question again...

Your car can use any octane above what is recommended by the manufacturer.

If you need RON 91, then you want to use RON 120 also can, but you don't gain any advantage except for psychological effect of using more "premium" fuel.

If you want to use lower octane like RON 88 also can, but you risk engine knocking which sometimes can be totally eliminated by retarding ignition timing, adjusting the valve timing.. of course you need a standalone ECU, factory ECU re-map or a piggyback ECU system to do this.

My engine states it needs RON 97 but we tuned it to run with RON 95 with marginal difference in power.