“Miles per gallon is misleading and can play tricks on our intuitions”
Duke University professors show experimentally what many of us have been saying for a while: talking about fuel consumption in terms of "MPG" is problematic.
Quote:
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(Duke) professors Richard Larrick and Jack Soll ran a series of experiments showing that the current standard, miles per gallon or mpg, leads consumers to believe that fuel consumption is reduced at an even rate as efficiency improves. People presented with a series of car choices in which fuel efficiency was defined in miles per gallon were not able to easily identify the choice that would result in the greatest gains in fuel efficiency.For example, most people ranked an improvement from 34 to 50 mpg as saving more gas over 10,000 miles than an improvement from 18 to 28 mpg, even though the latter saves twice as much gas. (Going from 34 to 50 mpg saves 94 gallons; but from 18 to 28 mpg saves 198 gallons).
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The authors then tested people by presenting fuel consumption ratings in the form of gal/100 miles, and the mistaken impressions were corrected.
Not surprisingly, the authors call for for a change in the way consumer publications and manufacturers report fuel consumption.
Full article:
http://www.dukenews.duke.edu/2008/06/GPMFuqua.html