[Racer-X-]

I don't know how it works in Europe, but here in the USA, corn fed pumps that say "E85" have some fine print that says something like "50% to 85% Ethanol by volume." It's rarely exactly 85% Ethanol. That's why "flex fuel" cars have a sensor in the fuel system to figure out how much gasoline and how much corn mash is in the tank.

Unless I was really sure that I was getting 85% ethanol all the time, I wouldn't assume you know the exact blend.

Here's the official US Government website that explains it:

Alternative Fuels Data Center: E85 (Flex Fuel)

afdc.energy.gov

E85 (or flex fuel) is a term that refers to high-level ethanol-gasoline blends containing 51% to 83% ethanol, depending on geography and season