Fermentation alone will only get you around 10% alcohol. You then need to distil (this is where the slang term "still" comes from) to seperate the alcohol from the mash. Alcohol has a lower boilingpoint than water, and therefore evaporates first.
Run yur car on Vodka. Personally, I'd rather drink the Vodka and pay for the gasoline. Then again, after drinking all that vodka, I'd be in no fit state to drive.
I also believe it's illegal in most places. Government can't get their taxes.
Down here in DownUnderLand, they want to outlaw home made BioDiesel for the same reason.
Amanda