1198, If you really want to use the lower grade of RON fuel, get a tunable ECU and retune it. But having said that the 1ZZ is very similar to the Altis/Corolla engine which minimum requirements are RON92 (Pls correct me if i'm wrong ya) so should be ok. My VIOS runs fine with RON95, mileage and all adds up, perhaps i feel that the engine has less breath, but I think it’s in my head only :-)
BTW i just tuned my RB25DET and RON95 works fine on the turbo engine, inface i did not lose power at all on the DYNO.