The big joke about corn ethanol as a petrol-substitute is that, depending on which university study you trust, every gallon produced has required the energy-equivalent of about a gallon of petrol - more or less, depending on whether the particular study was financed by the ethanol industry. And, as has been mentioned, the energy density of ethanol is less than petrol (just as that of diesel is higher). So you use the equivalent of about a gallon of petrol to produce a gallon of ethanol which will not take you as far. The distortion of the corn/ food market, pollution problems etc. are additional 'advantages' which the ethanol subsidies have purchased.