Thanks! I simply agree with you. Yes I think that the main advantage of higher octane rating is higher power, all other conditions remaing unchanged. Besides, it seems that during WW II the Allies including France had no problem producing aviation fuels with high octane ratings while the Germans seemed to have difficulties - remember the conspicuous yellow "87" on Me 109s. I wonder why for German chemists always were among the best in the world and this was no witch-business.