Smaller Engines, Higher Mpg

By John Eichberger | January 2016

Improving fuel efficiency is certainly a hot topic going into 2016. For one, it's a government requirement and two, consumers are demanding it. Will the answer be the introduction of sexy new alternative vehicles that promise 100 mpg? Possibly, but data suggests that traditional engines and fuels aren't going anywhere anytime soon.

The auto manufacturers are under incredible pressure to meet government regulatory requirements and satisfy consumer demand for more miles per gallon. But it may shock some observers that, while super-efficient alternative vehicles continue to make headlines, a lot of the hard work focuses on maximizing internal combustion engine (ICE) efficiency for vehicles that run on liquid fuels. (See "Don't Get Distracted," which evaluates the future for liquid fuels.)

Of course, the ICE has been around for more than 100 years, but if one were to challenge very talented engineers to maximize the ICE into a smaller, more compact and efficient space, remarkable things will happen.

Let's take a look at some numbers. According to the U.S. Environmental Protection Agency, fleet average mpg has gone from 19.3 mpg in 2004 to an estimated 24.7 mpg in 2015-an impressive 28% improvement. Most of this progress has been achieved through traditional ICE improvements, as well as direct injection (DI). Since model year 2011, DI-equipped domestic vehicles have increased from 9.1% of the market to 41.1%, according to WardsAuto. And while not as dramatic, manufacturers have increased their use of turbocharged engines from 6.9% in 2011 to 17.2%. These technologies deliver improved efficiency through the traditional engine structure.

We also know that smaller engines are becoming much more common in the market. According to WardsAuto, the use of 8-cylinder engines in domestic cars has dropped from 10.2% in 2006 to 2.9% in 2015, and 6-cylinder engines have dropped from a market share of 38.8% to just 13.2%. Meanwhile, reliance on the more efficient 4-cylinder engines has grown from 48.5% to 80.7%.

Similarly, 8-cylinder trucks also have given way to smaller engines. Domestics have decreased market share by 11.4 points, while imports are down 8.3 points of market share. Smaller 4-cylinder trucks have gained an additional 16.1 points of market share of the domestic truck market and 38.6 points of the imported truck market.

The combination of downsizing the traditional ICE, DI and turbocharging, among a number of other advancements, has enabled the auto industry to boost vehicle efficiency and deliver the performance consumers demand. Alternative vehicles and fuels have a definite role in the future of the transportation market, but as these technologies are developed and introduced to the market, the traditional ICE and liquid fuels market will satisfy consumer needs for fuel efficiency in the near term.

Read more from the January Issue of our Fuel for Thought newsletter.