I was reading somewhere recently--OK,OK, it was Reader's Digest again--that one way we could save a significant amount of gas is to lose weight. I don;t remember all of the details, but the logic was simple: On average, American's weigh about 20 pounds more today than they did 20 years ago. If we weighed the same as we did 20 years ago, our cars would be carrying aroun less weight and we all know that there is a weight/fuel consumption teade off holding all else equal, a lighter car consumes less fuel).
So, in true Env-Econ style, I thought I would do some quick, highly stylized, most likely innacurate, back of the envelope calculations--and then leave it to you to rip it apart.
Here we go:
First some data:
- Average weight of a gas-engine car: 4,000 pounds
- Average weight of an American in 2012: 178 pounds (assuming 50/50 men and women).
- Average weight of an Ameican in 1990: 158 pounds. ("Both figures are nearly 20 pounds higher than the average that men and women reported in 1990")
- Fuel consumption reduction for a reduction in weight: 2-4% reduction in fuel consumption for every 10% redcution in vehicle weight--we will assume 3%.
- Average fuel consumption in U.S.: 8.5 million barrels per day (357 million gallons @ 42 gallons per barrel)
- Average fuel consumption In U.S.: 130,305,000,000 gallons per year (357 million x 365 days/year).
Now for some calculations:
A 20 pound decrease in vehicle+driver weight from 4,178 pounds to 4,158 pounds is a 0.4786979% decrease in vehicle weight.
If for every 10% decrease in vehicle weight, fuel consumption decreases by 3%, then that 0.4786979% decrease in vehicle weight will result in a 0.14360937% decrease in gasoline consumption.
Given gas consumption of 130,305,000,000 gallons per year, that 20 pound reduction in average weight will result in a savings of 187,130,190 gallons of gasoline per year.
At an average price of $3.50 per gallon, losing an average of 20 pounds will save $654,955,665 per year--or $2.73 for every adult in the U.S. per year.
Enough to buy a non-fat, no-whip, skinny mocha latte--you know, to keep the weight off.
