Original sentence: Because gas consumption (and carbon dioxide emissions) are a curvilinear function of mpg improvements , it is easier to see the environmental benefits of trade ins by using a gallons per mile measure such as "gallons per hundred miles"
Edited sentence: Because gas consumption (and carbon dioxide emissions) is the reciprocal of mpg , it is easier to see the environmental benefits of trade ins by using a gallons per mile measure such as "gallons per hundred miles"