In Reply to: I have used it posted by Yukon Dave on November 12, 2000 at 14:22:07:
Because the DME won't keep advancing the timing up till the point it knocks. It will run the timing at whatever its maximum advance is programmed to be. As long as it isn't knocking it won't further adjust timing. Increasing octane past that point isn't going to make the DME advance the timing any further.
With lower octane fuel the DME will retard timing as needed to eliminate knock.