Thought I'd try V power.

[Dead Eye]

Given that a higher RON fuel has a more controlled burn, timing can be adjusted to make the most of the burn cycle to ensure you get the most out of the fuel? I'm not saying the fuel has more energy, just that the timing can be adjusted to make the most out of the burn. Given the more uncontrolled burn of a lower RON fuel, I would assume that at least some of the energy is wasted.

Engine design (and probably ECU software) will factor in a lot on this I imagine. I agree that an engine may not NEED a higher octane fuel to function, but surely that is like saying you don't NEED decent tyres - the car will still perform its function. But upgrading either can be beneficial - I'm not saying it definitively, just that it is possible.

I would guess that the most modern engines can probably get very good efficiency from the burn cycle of lower RON fuels, but that doesn't mean you can't edge out that little bit extra. I'm all for experimentation so I tend to base my recommendations on first hand experience - anything else is subject to (polite) scrutiny, theory and discussion until it is put in to practice. I've personally found that the ignition advancer has made my experience on my thou more enjoyable, but it has been extensively modified... YMMV