915iS Fuel

There is nothing wrong with <=10% ethanol in the fuel.

Both will power the engine just fine.

When dealing with a turbo engine, the higher the Octane rating the better.

93-E10 will pretty much guarantee that you won't see any water condense in the sump.

On the other hand, I will guess that the 91-E0 is going to cost significantly more.

In my area, E0 gas is Marketed to the boating crowd.

Noone has been boating in northern Ohio since last October so any E0 gas in the pumps has been sitting there for at least 5 months.

The 93-E10 is much more likely to have the pump tanks refilled a few times a week at a busy station.  Something to consider.

Thanks Bill, good thought.

I had the same question. In my area, the Ethanol-Free gas is available only in 90 octane, whereas the manual stipulates minimum 91. Brings up a few questions:

Would you recommend 93-E10 vs 90-E0, (because of the increased octate)?

With E10, you don't worry about the ethanol drying out the rubber components in the fuel system?

Would you prefer 93-E10 over 100LL + Decalin RunUp?

In my area, 91 E0 is sold by some gas stations as the only premium they sell (at about the same price as others are selling 93 E10) so it's not just to the boating crowd here.

There's actually more energy in E0 fuel (by volume) than E10*.  The ethanol does boost the octane rating, but that's not the same thing; anything over 91 is unnecessary in these engines.

I would always prefer unleaded fuel over 100 "LL".  It's much less expensive, not only in the base price, but also in added costs of Decalin (which just helps spew the lead into the air, instead of accumulating as sludge in the oil), and extra oil changes.  I understand that leaded fuel is needed for a lot of aircraft engines, but not for Rotaxes, and it's bad stuff, in more ways than one.

* Denatured ethanol contains about 30% less energy than gasoline per gallon

OK, so which would you prefer between 93-E10 or 90-E0?