I agree with Waynne to be honest. I've not used sueprmarket fuel for years, although I have recently tried Tesco's Momentum 99RON unleaded in the BMW. Seems OK to me but this car is pretty forgiving - it's a naturally aspirated 2.8 litre six and is in standard tune which slightly shy of 200bhp so it's not exactly over stressed.
BMW suggests 98RON for optimum efficiency so I thought I'd try the Tesco stuff. I don't think anyone needs convincing that a branded super u/l will be superior.