high octane might be diagnostic or precautionary if
experiencing engine 'knock' 'pinging' or pre-ignition..
unlikely for this engine,, but one possible reason for
using slow burning fuel [ie, high octane rated]..
our combustion chamber conditions are designed for
faster burning fuel, ie; lower octane rated petrol/gasoline..
ethanol is blended here [aust] with 'regular' [91ron/87pon]
thus motorists rejecting ethanol are forced to pay for 'premium'
[95/98ron] to avoid ethanol in their engines..
aside from older [carb etc] vehicles this also includes
many other motorists, according to the nrma..
ive used 95/98 in emergencies to avoid ethanol in 91ron
thing is, you just dont know how much ethanol is actually
in fuel labelled as '10%'.. could be less, or more..
storage tanks can leak or otherwise allow water in,
relying on mixing when tanks filled/topped up
thus in static stored petrol phase separation results in
dropping of ethanol/ethanol-petrol/water layers down
to bottom of storage tanks, which may be pumped out
into unsuspecting driver/rider tanks..
so it could be the luck of the draw what you actually get
as '10%' ethanol, and from storage tank conditions/turnover..
recommend using reputable outlets with good turnover
and zero ethanol added to any petrol stored/sold..
otherwise perhaps 95ron as ethanol 'free' emergency..
usa also has 'rec-90' pure petrol for marine, aircraft,
and other small engines..
[link = first hit google search; 'ethanol over 10% stalling']
List: E10 Engine Damage & Performance Issues.