Chemically, it's pretty easy to make a higher RON petrol with a few simple additives to delay ignition under compression and prevent pinking, and those additives don't necessarily make the fuel any cleaner, unless the "premium" fuel specifically states it has more detergents than normal.
Fuel is so clean from the refinery these days (ultralow sulphur fuels etc due to ever tighter specifications for Sox, in the EU at least), deposit build-up is a long process. A shot of treatment like Wynns periodically should keep the injection system for the equivalent of less than a penny per litre of fuel.
