Achieving Efficiency?

A look at on-road fuel economy changes over 92 years.

Although the whole 2025 CAFE fuel economy requirements may be removed by the Administration sometime soon, we can’t lose sight of the fact that global automobile manufacturers—which pretty much means almost any company that you can name at the drop of a hat—have to compete on a global basis, so unless the European Union and the People’s Republic of China decide to eliminate their forthcoming requirements, then improving fuel efficiency is a must-do for the OEMs.  After all, an increasing number of vehicles are being developed as global platforms, which helps reduce the engineering costs.  In addition to which, there are the advantages realized by manufacturing economies of scale.  Simply put: the more you make, the greater the return (assuming, of course, that people buy ‘em).

Two researchers who are diligent at keeping track of automotive technology, Michael Sivak and Brandon Schoettle of the University of Michigan Transportation Research Institute (, have recently looked at the on-road fuel economy changes across the fleet of vehicle types—cars, trucks, buses, and motorcycles—over 92 years, from 1923 to 2015.

They found that in 1923 the fleet fuel economy was 14 mpg.  But by 1973, that number was down to 11.9 mpg.  Any assumption that things just keep improving over time just isn’t necessarily correct (assuming, of course, that you think that fuel economy gains are considered to be an improvement).

But then there was that 1973 oil embargo, so there was a rapid increase in mpgs, they found.

That is, cars had an average of 13.4 mpg in 1973 (remember: that previous figure is for the whole fleet of vehicles) and it improved to 21.2 mpg by 1991.  However, by 2015 that 21.2 increased by only 2.7, to reach 23.9 mpg.

One of the things that the researchers think is important to do is to address the light vehicles—not those trucks and buses that are used for purposes of transport, commerce or other societal benefit (which can be assessed in terms of ton-miles per gallon and passenger-miles per gallon rather than straight mpgs)—that are comparatively low on the efficiency scale.

That is, if a car that gets 40 mpg is improved such that it gets 41 mpg and it is driven 12,000 miles per year, then the one mpg improvement in this situation results in saving seven gallons of fuel a year.

However, if a vehicle that gets 15 mpgs is improved to 16 mpgs and drives the same 12,000 miles, that results in a fuel savings of 50 gallons per year.

Let’s hope that going forward fuel efficiency improvements are not driven in a reactive manner as they were in 1973.