Hey Purple, I use high octane fuel because the higher the octane, the lower the combustion chamber temperatures. High octane is a small price to pay to keep our little air-cooled engines in their acceptable temperature zones, especially since I ask my TW to propel my 250 lbs as well as my "stuff" down freeways at 70 mph. To make matters worse, it get really hot here in Sacramento, CA in the summer.
Having read similar posts in the past, I'm sure there will be those who disagree. Enjoy!