I like cars, but I'm certainly no mechanic. So all I really know about fuel is that higher RON = better performance. No bad thing!
Now Shell have rebranded and tweaked their Optimax fuel - it's up from 98 to 99 RON, and is called V-Power. Frankly the name doesn't appeal and I preferred it called Optimax, but when I think about the clumsy mixture of "optimum" and "maximum" in that I cringe anyway, so perhaps I'm just a name snob.
Anyway, it'll be priced higher than regular fuel and hopefully help you coax out an extra few bhp from whatever engine you're running. I'll give it a try and see how it goes...