miles per gallon vs. liters per kilometer
About a year after my French friend Luc arrived in the states, he told me that he had basically adjusted to nonmetric units, with one exception, miles per gallon. In Europe not only do they measure fuel in liters and distance in kilometers, but they also measure fuel efficiency in liters per kilometer (not kilometers per liter). Clearly Luc is doomed, but as Matt points out (twice actually) the American approach is somewhat misleading.
If we assume that each month I drive 1000 miles (although my real total is much closer to zero), then a 27 mpg car (the current standard) requires 37 gallons of gas each month. A 37 mpg car, meanwhile, requires 27 gallons of gas, and a super efficient 57 mpg car requires about 17.5 gallons. Going from 37 mpg to 27 mpg saves about as much fuel as going from 37 mpg to 57 mpg, and from there going to 80 mpg only saves 5 gallons more.
Earlier this month my housemate and I were a little disappointed with the recent (and long overdue) 10 mpg increase in fuel efficiency standards (by 2020). Now I feel a bit better about the whole thing (although the EPA’s decision to block individual states from raising standards further is still ridiculous).