At the very end of the day unless your car is specifically mapped to use higher ron fuel, it is doing absolutely nothing to your engine apart from potentially cleaning it out due to the extra detergents in it.

Most cars 2000 on have a 'knock' sensor which adjusts the timing depending on which fuel you put in and when it detonates - these can compensate for higher RON fuel, however, it won't improve performance when using it.

Sometimes, you can see marginal MPG increases when using higher RON fuel in a standard car (Personally, my MPG is exactly the same if I'm using VPower, Ultimate, Momentum as it is if I use standard Shell, BP, or Tesco fuels. When I did see an increase it was because I had adjusted my driving style to see if I could get higher MPG with the premium fuel.

You'd be far better off spending less on regular fuel, and adjusting your driving style to boost MPG - unless of course your car is specifically mapped for the higher octane fuel.