Ethanol Usage
If you can find ethanol free fuel you are an exception and we all wish we could, but...
Ethanol laced 91 oct. is a far better choice over 100LL for your average flying just because of leading, not to mention all the extra maint. Rotax has published that 10% is okay to use because that is all they have tested, but in areas in Central and South America they use up to 22-23% ethanol and have been for many years without any issues. They just recently tore down a 1400 hr. engine and all was good. So the engine doesn't care. Our fuel hoses today are good otherwise all our cars would be parked and disabled along side the road. So if your fuel tank can handle the ethanol there is no REAL reason not to use it. Water absorption should not be an issue because it should not have anyway into the tank other than through a tiny vent hole or you poor it in and your fuel was trash to start with. I have demonstrated this by poring a class of water into a fuel tank and still running the engine. If you ever see standing water in ethanol fuel it's time to get rid of it because that means it is fully saturated. The ethanol can absorb water up to a certain point depending on volume and still run. Yes you do not want it in there and living a in a humid climate and worrying that the fuel will suck up enough water to kill the engine isn't realistic since it has to go through a tiny vent and the fuel is off gassing through that vent all the time anyway. I have yet to actually meet a person that had a proven case of phase separation. It's possible, but not very likely. Many areas in the world and the US use ethanol in the 912 and have been for many years without any issues. People tend to over worry.
I have heard all the claims about ethanol, but it hasn't been an issue for the ones that use it on a regular basis.
My guys at my field test every batch and we are supposed to have 10% here in Tucson, AZ, but it only really has 6-7% and the highest we have seen is 8%.
I'll use 91 Oct with ethanol any day over 100LL and all the lead damage it causes and all the extra maint. The only time I'm stuck with 100LL is when I travel.