Pascal, there are around 50 threads in this section which have discussed this subject in great detail, they vary from pure personal prejudice to complicated scientific explanation. I suggest you read through them, it is entertaining stuff, and then make up your own mind where you stand.
I have a chemistry degree and a Masters degree in Polymer technology, I am very familiar with the effect of various solvents including alcohols on rubber and plastics, and also to some extent the effect on metals. Brian works in the oil industry and has very detailed knowledge of petroleum products and also of motorcycle engines, yet we have different stances and opinions on this subject. Maybe a big factor for me, is that as a pensioner subject to negative exchange rate fluctuations since I came to Thailand, I have to spend my money carefully, and the gasohols are definately cheaper and in the 9 different motorcycles I have owned and run I have used gasohol for several hundred thousand Km, never noticed any deterioration in performance or fuel economy and have never had to spend anything on repairing any non evident damage from gasohol, so I have undeniably saved quite a sum of money and I will continue to do so, and by taking care of my money can still afford to buy new motorcycles now and then. Brian on the other hand, still working in the oil industry, can easily afford to use more expensive fuel, and also buy any new motorcycles he takes a fancy to, so the economic saving from gasohol is not a factor for him.
Have a good read and let us know what your conclusions are.