My 911 runs
much better on 100 or 110 than it does on 91. I was stuck having to use 87 one time, and it ran like crap.
OTOH, mine has all those whiz-bang electronics to take advantage of the octane
My VW bus doesn't seem to car what I put in it.
I think the only way to get more bang out of you buck with higher octane and not bumping up your CR is to advance your timing.