Whatever happened to water injection for emergency use?--Or the magnets for the proper fuel molecular alignment.
Maybe this is an issue with someone that is pushing for a best time in a drag race. But with a CR of 10.75 it seems like an unnecessary concern.
I have been running about that CR for 40 years with whatever gas I could find and have had no fuel related issues I know of.
If you really need 100 octane the best way to know you have it is to buy it. --You will never sleep well with mixes you are led to believe will give you what you seek. If for no other reason than it is a mix with whatever you have in your tank at the time of the "mix" or addition of the additive of choice.