I am going to offer a few thoughts here.
when a manufacturer states an octane rating for use in their motors that is the MINIMUM rating.
there is a point at which a motor does not benefit from a high octane rating and that usually affects motors with short crankshaft strokes and late ignition timing, why??
A high octane fuel is made to resist high compression pressures, advanced timing, boosted intake systems such as turbocharging or supercharging and in engines that are prone to preignition because they run at very high temperatures.
High octane fuel ignites slower and burns longer, the longer burn time is where the disadvantage is in short stroke motors as it is still burning at the bottom of the power stroke AND WILL POLLUTE THE INCOMING INTAKE CHARGE, this gets worse with higher RPMS.
I am not kidding you when I say I have tested and seen where short stroke motors will run harder and perform better with lower octane fuel.
So what about my two stroke engine and high octane fuel???
this is where it gets to be a science due to combustion chamber design, squish area in the cylinder head, piston shape, the surface speed of the piston, rod length, rod/stroke ratio, bore/stroke ratio, cylinder diameter and length of stroke and initial as well as total timing advance, all of this critical in all engines but two strokes are inherently more prone to it because of their small cubic inch displacement and higher max RPMS.
is your head spinning yet???
shoot, we aint even discussed air cooled versus water cooled yet and yes !! it makes a difference !!
point is, most two stroke outboards will run just fine on either 87 or 91 NON ETHANOL FUELS.
I would however stay with high octane fuel in supercharged outboards or any high performance outboards, and yes, I run the 91 non oxy in mine.
I must add, older outboards are not jetted properly to burn ethanol at any percentage, newer ones can as they are jetted for it or the computer controls the amount of fuel delivered in injected outboards.
for those of you who run ethanol and run lots of it all year and its as fresh as you can get, most likely you will be okay but never store it with ethanol as you will paying a shop a visit at some point in time.
my thoughts on additives, for those of you who believe the fuel company has your best interest in mind and personally cares for your motors as much as you do, keep drinking the purple Kool-aid !!
the additives in fuel today are only there to help promote combustion, ignite easier depending on the time of year, and at a minimum help keep things clean, remember, these are only used at the bare minimum to meet specs for each brand of fuel.
I wont cover the whole list of additives in gasoline as they number anywhere from ninety to one hundred twenty in number !!
Yes, there is a place for as The Famous Grouse calls them, snake oils, I do too depending on what you are talking about and even the good ones are over used, over rated, and certainly over sold.
I have my favorites just like everyone else and I use them as directed and only when needed.
there are circumstances where a whole sh!tload of them are needed but those are extreme cases and not the norm.
sorry for the long winded reply, my mind is not wired for short responses and most likely once again I derailed the thread.
