It is currently popular for automobiles to use 10% ethanol / 90% gasoline mixtur

Question

It is currently popular for automobiles to use 10% ethanol / 90% gasoline mixtures (‘gasohol’) as fuel. According to popular consensus the main benefit of gasohol use is that it “reduces our dependence upon foreign oil.” We test this assertion by making some elementary calculations. Our analysis will unrealistically ignore engine maintenance issues associated with older automobiles (such as gasket and seal hardening), added fuel consumption necessary to produce grain used as a feedstock in ethanol production, incremental food price increases associated with a reduction in grain stocks, and many other effects. Gasohol use typically reduces average fuel economy by approximately 15% and effectively leaves fuel prices unchanged. This article further debates the wisdom of ethanol use and may be of interest outside the problems:
http://harvardmagazine.com/2006/11/the-ethanol-illusion.html
These concerns and problems have been strongly influenced by conversations with Dr. H.J. Harmon, of the OSU physics department.

2. Consider a 14.2 mpg 1991 Ford F150 driven 761 miles. Calculate the pure gasoline consumption of this truck when: a) using gasoline, and b) when using gasohol (with its attendant economy reduction). Determine the total CO2 emissions for each fuel assuming all fuels produce 20 lbs of CO2 per gallon. Comment upon the wisdom of using gasohol versus pure gasoline in this vehicle.

Explanation / Answer

Prob miles mpg Gallons CO2 a 761 14.2 53.59 1071.8 b 761 12.07 63.05 1261 Note: 85% of 14.2 = 12.07 Pollution is more with gasohol and, although it's not mentioned here, price might be more expensive. Based on this only, gasohol is not the way to go.

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