Petroleum is a term usually referring to mineral oils produced by distillation from mined organic solids. Usually, pentane and heavier hydrocarbons are in liquid and solid form. This state makes them more stable source of fuel. On the other hand, methane, ethane, propane and butane exists as gases as they are lighter hydrocarbons. If you will observe, ethane has a chemical formula of C2H6 while ethanol has a chemical formula of C2H5OH. One hydrogen in the ethane is just replaced by a hydroxyl group (-OH). However, the usual way to produce alcohol is ethylene hydration and fermentation. Alcohol is more volatile than the heavier hydrocarbons, making it an unstable fuel source for regular cars, although it is already used as rocket fuel. On top of that, it is very difficult to distill a 100% alcohol. So most probably, you'll have water in it which you don't wanna have in your engine, unless you'll buy the one designed to utilize it as fuel. I think a car designed for such is already available in the market.
Puts a lot of stress on the motor. Alcohol will burn and work to run the motor, but it has a much lower ignition point, and is more explosive. And as Swebb said with the extra stress on the motor, it very well can go Kaboom :P.
not high enough compression for the motor to turn it will ruin your motor in no time unless it is built with over 12:1 copression pistons
i like your answer. thanks for it