In Reply to: I thought the specs were a minimum value? posted by John D. on March 02, 2001 at 08:53:29:
But then the car would be retarding its timing for 99.9% of all drivers. Possible, but unlikely. More likely the fastest timing (allowed by the stock chip) will optimize at 91-92 octane (M engines - otherwise figure a few points below the fuel recommended in the owners manual), and higher octane will not benefit you.
Note (again) that the retard function will certainly let you run lower octanes, but if the top octane anticipated is relatively low - as seems likely - you would not benefit.
I tried a bottle of high-quality octane boost at an autocross (quite illegal in stock class (blush)) a year ago. I could feel no difference from the 93 octane I usually run.
Now, if you have a turbo or supercharger, or an aftermarket chip that is optimized for higher octane (possible but unlikely), higher octane could help you. But in a stock car - no.
I guess the question is at one level does higher octane become less and less a factor.