Super Unleaded can make a huge difference, this is worth a read, it is about adjusting the timing to get the most from the fuel you are using.
It helps explain how much the timing needs to adjust between a 95 and 100 ron fuel.
The only difference on our cars, and most modern cars, is we have an ecu that monitors the fuel and adjusts the timing for you through knock sensors.
http://classicmechanic.blogspot.co.u...ern-fuels.html