Four-Cylinder Engines, MPG On The RiseBy Ivan Drury October 17, 2011
For consumers, its high fuel prices and slimmer wallets. For automakers, its the tug of pending fuel-economy regulations. Combine the two, and the U.S. auto market is undergoing a visible and predictable reconstitution, evidenced by smaller vehicles and smaller engines. A recent examination of data from Edmunds.com shows that over the last four-and-a-half years, the proportion of vehicles sold in the United States with 4-cylinder engines has climbed from 32 percent to more than 45 percent. In several recent months, the U.S. 4-cylinder engine mix has run more than 50 percent of sales, and the smallest engines now are established as the dominant choice in the market.
Edmunds.com data show that in January, 2007, 4-cylinder engines were fitted in 32 percent of all vehicles sold in the United States. By April of the following year, 4-cylinder penetration rates routinely passed the 40-percent threshold and have not been less than 40 percent for nearly two years, since January 2009. And so far this year, 4-cylinder engines have never accounted for less than 45 percent of all new-vehicle sales.
The markets shift to smaller engines means fuel economy is on the upswing, too. In January 2007, the average fuel economy for all new vehicles sold was 20.5 miles per gallon. When 4-cylinder engine penetration rates surpassed 40 percent in April 2008, average fuel efficiency had increased to 21.8 mpg. By March of this year, when 4-cylinder penetration reached 50.5 percent (one of the highest rates in four years), average fuel economy was 23.5 mpg 15 percent improvement from January 2007, when 4-cylinder engines were in just 32 percent of all new vehicles sold.
Stronger But Less Thirsty
Meanwhile, customers have sacrificed little, as new technology has markedly improved the power density of 4-cylinder engines, making them nearly as powerful and torque-productive as V6s of recent vintage. Turbocharging and direct-injection fueling have enabled displacement reductions even for 4-cylinder engines, and most engineers believe the costs of those new technologies largely are offset by eliminating two or more cylinders in the downsizing process. Ford Motor Co., for one, now has a turbocharged 2-liter 4-cylinder engine for its Explorer crossover, a vehicle that once was commonly fitted with a V8.
Even with increasing power levels, 4-cylinder engines are quickly improving their fuel economy. Edmunds.com data indicate that the average fuel economy for all 4-cylinder engines was 25.8 mpg in 2011. The average fuel economy for all 2012-model 4-cylinder engines is 26.6 mpg. Although the fuel-economy figure is influenced by other vehicle attributes and market mix, it is an indicator that 4-cylinder engine economy is improving in concert with increasing power densities.