Why you're not getting more miles per gallon

Posted by Kate Taylor

If you're an average motorist, you're driving a car that's vastly more fuel efficient than the one you had in 1980 - and an MIT economist has explained why it almost certainly doesn't feel like it.

Between 1980 and 2006, fuel economy of vehicles sold in the US actually increased by 60 percent. However, the average gas mileage  increased by just over 15 percent.

The reason, says Christopher Knittel, is that the average curb weight of those vehicles increased 26 percent, while horsepower rose 107 percent.

If Americans today were driving cars of the same size and power that were typical in 1980, the country’s fleet of autos would have jumped from an average of about 23 miles per gallon to roughly 37 mpg, well above the current average of around 27 mpg.

Instead, says Knittel, "Most of that technological progress has gone into [compensating for] weight and horsepower."

Knittel used data from the National Highway Transportation Safety Administration, auto manufacturers and trade journals to quantify just many Americans are buyingbigger, less fuel-efficient vehicles.

In 1980, he found, light trucks represented about 20 percent of passenger vehicles sold in the United States. By 2004, though, light trucks — including SUVs — accounted for 51 percent of passenger-vehicle sales.

"I find little fault with the auto manufacturers, because there has been no incentive to put technologies into overall fuel economy,” says Knittel.

"Firms are going to give consumers what they want, and if gas prices are low, consumers are going to want big, fast cars."
And between 1980 and 2004, gas prices dropped by 30 percent when adjusted for inflation.

Kittel argues that the best way to reduce emissions is through an increased gas tax that would encourage consumers to value fuel efficiency more highly - and buy more efficient vehicles.

In July, President Barack Obama announced new Corporate Average Fuel Economy standards  for cars and trucks, calling for a fleet-wide average of 35.5 mpg by 2016, and 54.5 mpg by 2025.

According to Knittel’s calculations, automakers could meet the new standards by simply maintaining the rate of technological innovation experienced since 1980, while reducing the weight and horsepower of the average vehicle sold by 25 percent.