Why Small Gains in MPG in Low Mileage Vehicles are Important
People greatly undervalue what small increments in miles per gallon (MPG) in large vehicles means and at the same time overestimate the value of increases in already fuel efficient vehicles. The right way to think about fuel efficiency is to look at gallons consumed per 100 miles according to an article in the June 20, 2008, issue of Science Magazine written by Richard Larrick of Duke University and a co-author.
Assume a family has a SUV that gets 10 mpg and are thinking of replacing it with a minivan that gets 20 mpg. They also have a sedan that gets 25 mpg and are thinking of replacing it with a hybrid that gets 50 mpg. Which replacement would save the more fuel? The answer is replacing the SUV with the minivan. With the SUV, the family has to buy 10 gallons of gas to go 100 miles while it would take 5 gallons to go the same distance in the 20 mpg minivan. The 25 mpg sedan requires 4 gallons to go 100 miles while the contemplated 50 mpg hybrid takes 2 gallons. So replacing the SUV saves 5 gallons of gas while replacing the sedan saves on 2 gallons of gas.
Larrick explains that the urgent need to save fuel is at the low end. He further explains there is a curvilinear relationship where the steep drops in fuel use occurs among vehicles that get mpg in the teens. The curve flattens out as vehicles become more efficient.
