I have over 20k miles on my f800, almost all of it was 89 octane with 10% ethanol..... guess what? No cracked fuel tank and the engine is still kicking! I do run BMW FI cleaner every erl change or 2500 miles. I am lacking in petro engineering but shy of some issues with some FI components early on and the fact that ethanol fuel per quantity lacks the efficiency and it likes to absorb water it isn't going to bog down a machine that was designed to tolerate it. Or perhaps I have a mystery machine that runs fine with proper servicing? Well I am going to go back to my fermented grain (currently being consumed in heavy quantities by my mouth).... There has to be a petro engineer among us?