Here's what I learned about E10:
It's likely about as energetic as regular fuel (the chemical energy reasoning falls short due to side effects).
Its Octane Number is higher than regular fuel due to ethanol's Octane Number.
It burns cleaner (less coking) and also has a cleaning effect - again due to the higher ethanol content.
It's hydrophile qualities are actually an advantage as that means it binds water which is entering the system.
Some gas stations sell regular as E10 (and then cheaper) because it isn't economic or possible for them to have yet another type of fuel in reserve.
The reason why oil industry hates E10 is because it is more expensive for them while by law (in EU) they are forced to sell it cheaper.
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There's only one catch which I still didn't wrap my head around.
My Mazda brings 160k kms to the table and features a "maintenance free" in-tank fuel filter which is somewhat difficult to replace. Now I'm a bit worried that using E10 will release built up residue attached to the tank and clog the fuel filter. And I don't know how fast this would take place.