Actually I have often wanted to run an oil temp gauge on the FZ6 because the Sporty oil runs that cool and I would like to see if the FZ6 does as well. The issue with air cooled falls back on combustion chamber temperature and not necessarily overall engine temperature.
I follow the manual and run 87 Octane. No knock problems so no reason to spend the extra cash. I get right at 45 mi/gal, but my fist tank was considerably less than that. Engine breakin I guess.
I have always been running 89 in my tank. I once fueled up with some 109 octane and got no better MPG and maybe a extra horse or two but its not worth paying the extra money for it tho.