To make it even murkier, while 'muricans use miles per gallon to measure fuel efficiency (higher numbers are better), europeans measure fuel consumption using liters per 100 kilometers (lower numbers are better). Doing the math tells an interesting story. Take a 30mpg sedan vs. a 15mpg pickup. We would say that the sedan is twice as fuel efficient as the truck. But if we want to decrease each vehicle's fuel consumption by 1 gallon over a 100 mile trip we need only boost the truck to 18mpg, whereas the sedan would need to hit 43mpg to save the same gallon of fuel. Fuel consumption is a linear scale, while efficiency sees diminishing returns the higher it goes.