on the contrary sir; read the instruction manual; the recommended fuel is 96 ron. our supreme in pakistan is rated at 90 ron. however i sincerely beleive its much below that rating esp with PSO and shell. the hi-octane rating in pak is 98 ron; wich actualy wud b sumwhere around 95 ron.
i have a 2010 swift, wnehever i fill the tank with hi-octane; which is mostly all the time, i have had much better mileage from wen i used to use supreme only. the car does not knock, does not stall and is generally much smoother and more silent.
read the instruction manual; the swift is a hi-octane car..in the process it gives better mileage than supreme and if u calculate u end up saving in terms of mileage