[Porsche-O-Phile]

What's the octane rating of the "pure" non-ethanolized gas?

Doesn't the addition of the 10% ethanol add to the octane rating? This came up (I think it was Tim Hancock who pointed it out) when I brought up building an ethanol extractor (which I have collected some of the materials for BTW, so the project is going ahead...)

I thought also this was part of the issue with the impending ban on leaded AvGas - you can't get the 100 octane rating without either lead or ethanol (or methanol, or some kind of alcohol).

Anyway, the point is that the implication here is that the refining of the gasoline part is of a lesser quality, relying on the E10 to boost it up to 87, 89, 91 or whatever... Anyone know for sure if this is the case and if so, how much of a difference we're talking about?