ANN ARBOR, Michigan — A new study from the University of Michigan Transportation Research Institute takes a historical view of vehicle fuel economy in the U.S. from 1923 to 2013 and reveals dramatic increases beginning in 1974.
But there's a catch. Researchers note there's been little progress since the early 1990s.
"Despite steady advancements in fuel-saving technologies in the last 25 years, on-road fuel economy for all vehicles has improved by less than a mile per gallon during that time — partly because it takes many years to turn over the fleet," UMTRI said in a statement on Monday.
UMTRI researchers Michael Sivak and Brandon Schoettle found that, in general, average fuel economy stayed around 14 mpg from 1923 through 1935, then declined gradually to 11.9 mpg in 1973 before increasing sharply to 16.9 mpg in 1991 and finally improving steadily to 17.6 mpg in 2013.
"After the 1973 oil embargo, vehicle manufacturers achieved major improvements in the on-road fuel economy of vehicles," Sivak said. "However, the slope of the improvement has decreased substantially since 1991."
Although average fuel economy has been represented differently over the years through various combinations of vehicle classes — heavy trucks, light trucks, cars, motorcycles — the researchers compiled data from the U.S. Department of Commerce, the National Safety Council and the U.S. Department of Transportation to take a detailed look at overall historical trends.
Not surprisingly, the onset of the most dramatic increase coincided with the first OPEC (Organization of Petroleum Exporting Countries) oil embargo in 1973, which saw prices rise from $3 per barrel to nearly $12 within about a year.
The higher oil prices caused the U.S. retail cost of gasoline to shoot up from an average of 38.5 cents per gallon in May 1973 to 55.1 cents in June 1974. The wide-ranging effects included a 55-mph national speed limit, demand on the part of consumers for more fuel-efficient vehicles and, ultimately, government fuel economy standards that continue today and reach into the future.
The study is quick to point out that the decline in fuel economy in the 1935-'73 period "does not imply that powertrains for vehicles have not improved during this period. Instead of focusing on fuel economy improvements, engineers focused on increasing power and acceleration."
According to Energy.gov, gasoline prices averaged from 19 cents per gallon in 1935 to 36 cents in the early 1970s. As a result, most consumers at the time were more interested in power, comfort, style and vehicle features than in fuel savings.
But when gas prices spiked, demand increased for economy models like the Chevrolet Vega, Dodge Colt and Ford Pinto, as well as imports such as the Datsun B-210, Honda Civic, Toyota Corolla and Volkswagen Golf (sold in the U.S. at the time as the Rabbit).
Today, the quest for fuel economy continues, with hybrid models like the Chevrolet Volt, Ford C-Max Hybrid, Honda Civic Hybrid and Toyota Prius delivering up to 50 mpg, a figure that would stun some mid-1970s drivers.
Even many of the latest gas-only models — including versions of the Chevrolet Cruze, Ford Focus, Honda Civic, Mazda 3, Nissan Sentra, Toyota Corolla and Volkswagen Jetta — are capable of returning 40 mpg, while providing levels of comfort and performance that top those earlier economy cars by a wide margin.
So where do we go from here?
The latest federal regulations require that automakers meet a CAFE (Corporate Average Fuel Economy) standard of 54.5 mpg for light vehicles by 2025. And, as previously reported by Edmunds, for the past three straight years they have surpassed interim targets, putting them well on the way to reaching the ultimate goal.
To remain on track, the UMTRI report suggests that manufacturers concentrate on what it calls "the lower tails of the distributions of fuel economy in each vehicle class. In other words, society has much more to gain from improving a car from 15 mpg to 16 mpg than from improving a car from 40 mpg to 41 mpg."
They said an improvement from 40 mpg to 41 mpg for a vehicle driven 12,000 miles per year saves seven gallons of fuel a year. But an improvement from 15 mpg to 16 mpg for a vehicle driven the same amount of miles saves 50 gallons of fuel a year.