Mogas or avgas

Hi James,

In Australia we tend towards standardised terminology, when describing petrol  types.

By law, fuel sold with an ethanol content must be so described. A petrol with the letter E indicates an ethanol content eg E10 which contained up to 10% ethanol. Supposedly E 85 (for very specific vehicles) is available but I have never seen it.

Non ethanol fuels are simply 91 RON, 95 RON and 98 RON. (RON = Research Octane Rating) 95 & 98 RON are suitable for Rotax 912's

The above descriptors are standardised across all states (there are some geographically specific fuels)

It would seem that in the USA you have all sorts of descriptors, (clear, non ethanol, mogas, marine, winter/summer, gas, ??)  which seems to lead to some confusion. Added to this is the winter/summer blends, causing further complication.

Ethanol has a higher knock/Octane rating than petrol but a lower energy content. So octane rating unlikly to be an issue however users of ethanol blends, will find that their engine delivers slightly less power than non ethanol fuel.

Rotax allow the use of E10 in their engines. To take advantage of this, the whole of the fuel supply system, to the engine, must be ethanol compatible. I do not know of anyone using E10 in their aircraft.

"Is 92 octane clear exactly the same as 92 octane mogas except without the ethanol"

Speculation:

If its 92 Octane, with or without ethanol,  it can be used in your Rotax. If it containes ethanol, you need to check with your aircraft maker for the fuel supply system compatibllity.

If in doubt, avoid using ethanol fuels.😈