What does Vans mean you can use avgas with a little tweaking of the engine and will gasoline with ethonal in it affect the componets of the engine.
From Rotax and others, E10 seems to be Ok if the aircraft's fuel system is up to it (fuel tank, lines, etc). Given the choice between lead and EtOH, you're probably better off using the E10 gas and not putting lead into the engine.
100LL won't harm the aircraft, but it does mean shorter time between oil changes and lead will accumulate in the engine, particularly in the gearbox.
TODR
Given the choice of 87 octane or 100LL, you must choose 100LL.
87 Octane will run just fine in a 912 if that is all you have. If the octane level concerns you mix 87 & 100ll. It is the lead you are trying to avoid, not the octane level.
I sure wouldn't use 87 in the 100HP rotax either. Mixing with 100LL is an option if anyone knows the mix ratio. Rotax parts are expensive so why chance engine damage and worse?
The rotax manual says 91 octane is fine so you don't need 92.
I strongly recommend RV-12 owners do NOT use fuel with an octane lower the what is recommended by Rotax (92 octane).
Larry,
I need to disagree with you. There is nothing in SI-912-016 that says it's OK to run 87 in an engine where rotax specifies 91. What the SI is saying is that they want you to run the appropriate grade of mogas if it's available. For the 80 HP that means 87 octane or better but for the 100 HP its 91. If you put 87 in the 100 HP you are going to end up doing damage. This is my opinion. Unless I see something in writing from rotax, I would never put 87 in my 912 ULS. Let us know how your engine is doing after running 87 for about 10 hours, especially on a hot day.
If you mix it using the correct ratio, which I don't know what that is, then I agree.
I'm no expert on fuel for the Rotax 912S, I just don't want people to get the idea that these engines cannot go cross country due to the lack of mogas. I have made many cross country trips and have never had any problems getting fuel, or causing damage to an engine because of my fuel choices. Most people say just use 100LL and IMHO that is not the way to go. I have seen first hand the deposits lead makes in the gear box, oil tanks, journals having replaced the sprag clutch & spring assembly in a 912S. Use mogas when you can and use 100ll sparingly to avoid lead deposits and sediment in the engine.
JMHO.
If AirNav.com is at all accurate:
Fuel prices within 100 miles of KTZR
NOTE: No Mogas (auto) found in the area