915iS Fuel

Thanks to all for the insights.  I decided on 91 AKI, E0 and have had very good performance and no issues with now 20 hrs flown. Fortunately, I have a Quick Trip that carries this fuel just outside the airfield (KOJC) entrance. 

915iS published minimum octane is 93 and can contain up to 10% ethanol. Premium unleaded at a reputable service station the best fuel. Any octane lower voids your warranty. Carefully examine MOGAS pumps at airports as octane can vary between 87-93. A way to increase octane of low octane MOGAS is to add the appropriate amount of 100LL to make up the difference. Burning 100LL reduces maintenance intervals due to lead. Rotax engines were designed for unleaded fuel. Rotax is positioned to run the newer unleaded aviation fuels to enter market. - Certified Rotax Technician

The published minimum AKI (the "octane" number used for auto fuel in the US) is actually 91, NOT 93.

See Operators Manual, Rev 2, Section 2.3.

93 AKI "mogas" invariably contains ethanol.  91 is generally the highest AKI rating available with no ethanol (assuming no other additives (eg MTBE or TEL)).

There is no 93 "Octane" mentioned in the Operators Manual.

As Tyler mentioned the requirement is for AKI 91.
The other spec mentioned in the manual is for RON 95 fuel.
Both are equivalent.

I always "heavy" up my fuel trailer in the spring with 10-20% 100LL. This helps keep the fuel from boiling in the lines before all the "winter blend" fuel has been used up from the previous winter months. Since the amount of 100LL is so small the amount of lead doing this is also quite a bit smaller per volume. A win in my column. And if you're using E10, this also reduces the ethanol content per volume as well.

Plus it adds to the octane. Even though Rotax specifies minimum octane at 91AKI, I'm sure you can tell that they run much smoother with 100LL in them.

Can't wait until they get the 100 no lead into the supply chain!