Ran into a Science Daily article about some research done at Duke that suggests specifying fuel efficiency in terms of gallons per mile instead of the usual miles per gallon may help people understand better how fuel economy changes as the numbers change.

the current standard, miles per gallon or mpg, leads consumers to believe that fuel consumption is reduced at an even rate as efficiency improves
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).
These mistaken impressions were corrected, however, when participants were presented with fuel efficiency expressed in gallons used per 100 miles rather than mpg. Viewed this way, 18 mpg becomes 5.5 gallons per 100 miles, and 28 mpg is 3.6 gallons per 100 miles

I wonder if the researchers realized that this is how fuel economy has been specified in most of the rest of the world for years (albeit in terms of l/100 km).