Headscratch.... Mmm- BP optimal is 97 an shell 98 is available at the pumps in the UK an is not considered as race fuel.
In fact a supermarket chain called Tesco offers 99 octane.
I used 105 for hill climbs 20 yrs ago and that was the stuff
I recently interacted with Terry from the states to design a custom pump fuel map, and his response was "What fuel are you running? your car needs a min of 95"