i got interested in higher octane gas after my spark plugs were changed at 32000 mils and I started pinging on 91 octane chevron/shell fuel. No problem prior. So I am beginning to check if differing spark plugs are used, differing gap or what. For now I am happy just to blend so I do not get any detonation.
Yes its damn $$$, best thing I think is suncoco/VP fuel in 54g drum and share the cost and use enough to get about 95 octane in the car. Both fuels are widely avail but shipping is costly, check out each web site and call the distributors and ask for reatilers in the area. If you have even a small race track in the area, you likely have a retailer nearby.