912 IS Sport - Fuel

[Monty]

I'm looking to hear if most everyone is using straight 100LL in the 912 IS Sport or how many are using an additive to the fuel to remove lead.
Thank you for your comments.

[aviator79]

You must use the additive if you run 100LL. That's not really optional. Kitfox and Stick and Rudder run exclusively 100LL with Decalin additive.

[Monty]

Thank you very much for the reply

[NinerBikes]

Other than the inconvenience of fueling up, it says here that the 912iS is capable of being run on 91 octane premium MOGAS.

https://www.flyrotax.com/produkte/detail/rotax-912-is-isc-sport.html

[aviator79]

...and up to 10% ethanol I believe. But: Ethanol is hard on the rest of the fuel system, and while the current tanks are supposedly ethanol-resistant, several horror stories are out there about fuel system contamination when running ethanol. There are others who have run hundreds or thousands of hours with ethanol fuels with no ill-effect.

Then there is the issue of vapor pressure. Mogas vaporizes much more quickly, leaving it's additives behind. You can't let it sit like you can with 100LL.

So if you have access to 91 octane ethanol free fuel, and burn it regularly, it's your best option. But for many (most?) It isn't practical.

[Billiken]

I’m slowly getting back up to speed in General Aviation. I’m in Florida and stopped into an FBO to check things out. I like to compare fuel prices and it was just under $5 a gallon for 100LL. Then I got a glimpse of something I hadn’t seen before. UL94. Apparently that is the high octane mogas offered by Swift. I stared at the price perplexed, $7.80 a gallon?! Way more expensive than 100LL! I’m just thankful it’s available at the airport. I wonder if the state of Florida is taxing it because it’s equivalent to 99 octane auto fuel. I researched it a bit and just recently announced that they would be changing the color from clear to purple. Swift Fuels, which produces UL94 avgas, announced in early March 2024 that all shipments of its 94 octane, unleaded aviation gasoline will be dyed purple.

$187 for a tank full of purple fuel. I’m inclined to ponder my Rotax obsession.