Thanks for the link. I value only hard data... not testimonials.
I used to have a 57 Chevy with an L-6 engine. At the base of the distributor was an an adjustment for octane. You could move the distributor until the pointer was at the octane you were using at the time. Basically it was just a gauge that allowed you to advance or retard the ignition timing.
95 E320 Cabriolet, 131K