My Mrs has a 58 plate SSS,and they told her at the dealership that up to a certain reg,the car had to be run on high octane fuel,but i think that my Mrs one says on the fuel flap 98+ octane,but il check.
Iv told her since she got it to run it on super,and she even tells me when she occasionally has to put normal stuff in,and the car is performs badly,so that puts her off anyway. She puts in Tesco 99.
my swift sport is run on normal shell fuel save stuff constantly and runs a treat.