Yes, the ethanol content can go anywhere from 70% to 90%. But then again, gasoline at the pump can go anywhere from 0% to 15%. That's why we have o2 sensors. If it's lean, it will adjust richer, etc. Since they are reading the result of the burn and not the a/f mixture itself, the o2 content is the same. So it works exactly the same.
(I'm here all week folks!)
