In an effort to boost fuel economy, automakers have cut the weight of vehicles by eliminating spare tires -- even as their customers have been adding spare tires of their own.
According to the federal Centers for Disease Control and Prevention, the average adult male is 28.4 pounds heavier since 1960, while the average female is up 24.5 pounds. Those are about the same weights as a tire for a Ford Mustang (male) and Chrysler minivan (female).
The EPA's National Vehicle and Fuel Emissions Laboratory in Ann Arbor, Mich., estimates that the theoretical couple's 53 extra pounds might cut vehicle fuel economy by as much as 1 percent, depending on the vehicle, on that drive to pick up a Big Mac and fries.
At a nationwide average price of $3.29 per gallon, that's about $503 million in additional fuel costs just in the last year.