at club track days we stick a partial mix of racing fuel 103RON in just for saftey, just being extra careful to prevent pinging/detination... it runs fine, doubt its got anything to do with the higher RON rating...
So how much extra is the this Optimax Extreme compared to normal Optimax?
I'll use whatever fuel my tuner tells me to (and tunes the car for).... and for now its 98RON. Plus i don't have a shell fuel card