It’s no myth that the increased use of corn for ethanol production has raised the price of corn used as food—increased demand causing higher prices is basic economics. The corn used for an increase in ethanol production here in the good ol’ USA several ten years ago was largely taken out of exports, and it was no coincidence that in 2007 the price of tortillas in Mexico skyrocketed.
However, my main gripes about ethanol production here in the good ol’ USA are (1) it’s only profitable for the producers because of taxpayer subsidies; (2) it’s diverting a crop normally used for cattle feed or human food to something else; and (3) whether the amount of energy obtained from the ethanol produced is as much as is used to produce it, is highly questionable.
The second concern would be alleviated if alternate “feedstocks” for ethanol production could be developed economically.
Anyway, back to ethanol in cars. The only two concerns in that regard I am aware of are (A) less lubrication in the cylinder as compared to that provided by purely hydrocarbon gasoline, and (B) burning a gallon of ethanol only produces about 2/3 as much energy as burning a gallon of gasoline. In earlier threads, MMO has been offered as a way to alleviate concern (A).
As to concern (B): Cheerfully disregarding non-linearities of relative volumes in mixtures, a rough-and-ready estimate predicts that 10% ethanol would reduce mileage by 3.33%, and 15% ethanol by 5% compared to hydrocarbon gasoline. Applying this to this to skyraider‘s statement that
filling up at 3/4 tank of 85 ethanol, the gas mileage drops from 15.5 to 12 mpg
is a little tricky, because I don’t know whether the 15.5 MPG is based on pure gasoline or 10% ethanol. Assuming it’s based on pure gasoline, the rough-and-ready estimate gives a reduction to 12.2 MPG. Assuming 15.5 MPG is from 10% ethanol, the rough-and-ready estimate is 11.95+ MPG.