The only reason ethanol gasoline exists is because of the government mandate . If we just let the markets figure it out it would disappear overnight . First , it is chemically a less efficient fuel . About on average , so it uses more gallons to get the same output . So it might be cheaper to put in your car , but you use more of it to go the same distance . Measure your gas mileage on a tank of regular 87 octane vs 87 E 10 . You ' ll be surprised . Second , the alcohols ethanol are hygroscopic as in it absorbs water . Fuel injectors meter out fuel by volume , so the higher percentage of your fuel that is water , the more your engine computer has to compensate for less fuel with timing changes and other adjustments based on oxygen sensor readings . This makes it even less fuel efficient than the 71 % compared to gasoline . Third , ethanol is corrosive to rubber and other things in engines . Plastic intake manifolds , gaskets , hoses and lots of other little parts . So engines tend to fail faster if they aren ' t specifically built to handle ethanol . Fourth , because of the subsidies , the price of corn goes up when farmers grow corn for ethanol production because the government says they have to and then pays them for it . So the price for other things that farmers could have grown regular crops also goes up . Corn , soybeans , wheat , etc . all go up in price , which makes food more expensive for everyone . I don ' t know what has changed in the last 8 ish years as far as production efficiency I ' m assuming a lot , but when I was in undergrad , it cost 1 . 1 gallons of gasoline to make 1 gallon of ethanol . this was due to transport multiple times between field to refineries , to mixing etc . I ' m assuming they have gotten better at it . Overall I hate it . I ' m all for alternative energy but ethanol is not the way to go . From lots of perspectives . Even financially unless ethanol is 30 % cheaper at the pump than regular gasoline it doesn ' t make any sense to buy it . Source College in Iowa , plenty of schooling in chemistry , and overall gearhead . Doesn ' t make me an expert by any means , and I ' m open to discussion . But I don ' t think anything I ' ve said here is wrong .