Fuel economy for on-road vehicles is slowly on the rise, but for the five decades prior to the 1973 Arab Oil Embargo and federal regulations that followed, the average actually decreased.
Perversely, efforts to improve vehicle mpg have come largely after threats forced automakers to change, and even then, the industry has focused more on what may have been the wrong end of the vehicle spectrum, suggests new research. That is, automakers have been intent primarily on making already efficient cars more efficient, rather that doing all that’s possible to improve the worst mpg offenders, and thus saving even more fuel
These are a couple of the take-away points from a study conducted by researchers Michael Sivak and Brandon Schoettle of the University of Michigan Transportation Research Institute.
The study – “On-Road Fuel Economy of Vehicles in the United States: 1923-2013” – examined relevant available data to determine fuel economy trends for various classes of vehicles.
The researchers suggest that as demand for bigger and faster vehicles naturally happened, and in the absence of regulations now clamping down, automakers driven by free market forces and readily available petroleum gave customers what they wanted at the expense of fuel economy.
Even today, automakers are playing the rules in “horsepower wars” where 400-700 horsepower is considered just-impressive, and the most-powerful supercars boast 800-1,500 horses – albeit some of these are now able to be nursed through a drive cycle by hybridization to satisfy regulators.
You might want therefore to bookmark this study if you’re a plug-in advocate for the next time you hear someone arguing regulations should lighten up, and the free market will naturally go electric and toward more efficiency all by itself.
Ninety years of history suggest otherwise.
Looking at all vehicles, the researchers ascertained that from 1923-1973 fuel economy decreased from 14.0 mpg to 11.9 mpg, but then the 1973 Arab Oil Embargo shook Americans up.
“Starting in 1974, fuel economy increased rapidly to 16.9 mpg in 1991. Thereafter, improvements have been small, with fuel economy in 2013 at 17.6 mpg,” says an abstract from the research.
From 1923-1935 that 14.0 mpg was relatively constant, says the research — fuel economy did not change much, but then demand for more power came
“Starting in 1936, fuel economy gradually declined, falling to its lowest level, 11.9 mpg, in 1973—the year of the first oil embargo,” says the study. “Starting in 1974, fuel economy increased rapidly to 16.9 mpg in 1991. Thereafter, improvements have been small, with fuel economy at 17.6 mpg in 2013.”
Passenger vehicles followed a similar trend to the whole vehicle market. From 1936-1973, on-road fuel economy dropped from 15.3-13.4 mpg.
From 1973-1991 fuel economy jumped, augmented not just by the wake-up call of the Arab Oil Embargo but also the first Corporate Average Fuel Economy (CAFE) standards for new light-duty vehicles enacted in 1975 and effective with 1978 model vehicles.
After that initial spike, since 1991 improvements were small, with fuel economy at 23.4 mpg in 2013.
The study does not attempt a comprehensive analysis of all variables, and indeed this would be a daunting task.
Rather the researchers observe that while powertrains did improve from 1935-1973, demand for increased power and acceleration weighed more heavily, taking a toll on fuel economy.
After 1973, an immediate 51.9 percent improvement followed from 12.9 mpg to 19.6 mpg for the period of 1973-1991.
“On the other hand, from 1991 to 2013, fuel economy improved by only 10.2 percent (from 19.6 mpg to 21.6 mpg), representing a compound rate of improvement of 0.8 percent per year,” say the researchers.
Does this mean internal combustion technology is reaching a point of diminishing returns? Or did automakers not see the need to try harder? The researchers do not offer any opinion.
What they do say is changes happened slowly also because there are over 252 million vehicles on the road, and each new vehicle stays in service so many years.
Older, or less-efficient vehicles keep the average lower even as new more-efficient vehicles are added to the fleet.
Turnover is slow, and the researchers observed the 16.5 million new passenger vehicles bought in 2014, for example, accounted for just 6.5 percent of all passenger vehicles on the road.
Started at Wrong End of Fleet
The researchers also posit what has been said many times before, that the most petroleum will be saved making gas guzzlers more efficient, rather than improving the already best fuel sippers. The absolute biggest fuel consumers are large tractor trailers, and larger and medium, and even light-duty trucks like pickups and SUVs all stand to be improved.
As former GM Vice Chairman Bob Lutz was once quoted as saying of the Chevy Volt, the industry is starting on the wrong end if it wants to take a 40 mpg car and improve it, versus a 14 mpg pickup truck, for example.
“Consider the following two scenarios, each involving 12,000 miles of driving per year,” say the researchers. “In the first scenario, an improvement from 40 to 41 mpg yields a reduction of about 7 gallons of fuel per year. In the second scenario, an improvement from 15 to 16 mpg yields a reduction of 50 gallons of fuel per year.”
Even greater fuel savings would be seen by bearing down on heavy and medium duty trucks, buses, and other vehicles, suggest the researchers.
Meanwhile, the U.S. has scant little hybridization or electrification of larger vehicles, and CAFE is otherwise holding manufacturers feet to the fire.
They are doing what they have to, in cases going above and beyond, but in many more cases not necessarily doing all that they could do to reduce petroleum consumption in the United States.
So it goes.