The octane rating is in no way an indication of how much power there is in
Ethanol have an octane rating at about 120. But gallon for gallon, you get less bang for the buck, compared to gasoline.
The octane rating is just a number telling how fast the fuel will burn.
Higher number - slower burn. Slower burn means you can have higher compression. Higher compression means you can get more power.
Lower number - faster burn. That also means easier to self-ignite. Or knock, as some might call it. :-)
So, gasoline with different octane ratings have about the same energy content, or power. (It's all gasoline, after all.) But how easy, or
hard, it is to get as much of that power out, differs. And also how fast you can extract it without getting all of it more or less as heat (which
won't do you much good).
And this is what Porsche says about E10 fuel~
Informationen zur E10-Eignung .pdf