Class 8 engine sizes shrink as emissions rule changes loom

Study shows downsizing to accelerate ahead of strict greenhouse gas regulations

The size of engines powering Class 8 tractors is expected to decrease as fleets seek to reduce fuel consumption and meet three rounds of strict federal emission requirements in the next decade.

The size of engines powering Class 8 tractors is expected to decrease as fleets seek to reduce fuel consumption and meet three rounds of strict federal emission requirements in the next decade.

Engines over 10 liters (L) are projected to account for more than 85 percent of Class 8 truck production between 2020 and 2024, according to a study by ACT Research and Rhein Associates.

“Although the over 14L engine category will remain the largest segment in 2019, there is a trend to smaller displacement engines in the over-10L market segment,” said Tom Rhein, president of Rhein Associates. The push is being prompted by federal greenhouse gas (GHG) regulations in 2024, he said.

In August 2016, the U.S. Environmental Protection Agency (EPA) and the National Highway Traffic Safety Administration (NHTSA) finalized Phase 2 standards for medium- and heavy-duty vehicles through model year 2027. The stricter regulations are intended to improve fuel efficiency and cut heat-trapping GHGs that cause a warming of Earth’s surface and the air above it. 

FreightWaves SONAR COMPP.USA data showing CO2 emissions generated by commercial vehicles over a 10-year period support findings by the Global Carbon Project that showed emissions reached an all-time high in 2018 (Chart: FreightWaves SONAR)

Global carbon emissions reached an all-time high in 2018, according to a December 2018 report by a consortium of researchers known as the Global Carbon Project.  

Medium-duty trucks also face tougher standards. Offerings of gasoline-powered trucks are rising. Isuzu Commercial Truck of America and Mitsubishi Fuso, a unit of Daimler Trucks, both introduced gasoline-powered Class 5 trucks in March this year. 

“Diesel power is under attack long-term for use in on-highway commercial vehicles,” said Kenny Vieth, ACT Research president. “Alternative power is being developed, tested and refined, even as diesel engines are transitioning to become more fuel-efficient and clean.”

The shift to hub-and-spoke freight patterns covering shorter distances to meet demands for faster deliveries could lead to the adoption of smaller-displacement engines, said Bill Van Amburg, executive vice president of Calstart, a clean transportation nonprofit.

“There is also a steadily growing regional goods distribution trend, all of which can make use of smaller bore engines in a Class 8 truck,” Van Amburg told FreightWaves. 

“It is not even the emissions concerns as much as the maintenance and engine expense,” he said. “While diesel engines last longer, they are more expensive and the after-treatment systems have been a maintenance issue for medium-duty fleets.”

Data confirms the move to smaller-displacement engines, said Antti Lindstrom, an analyst with IHS Markit. 

“Fuel economy is better while performance is too, so it’s a win-win situation for all,” he told FreightWaves.

California’s intention to get diesel trucks off its roads by 2035 gets a lot of attention. But other areas, including Portland, Oregon, are adopting tougher emission restrictions, Vieth said.

“We continue to see reports about state- and federal-level funding for alternative fuel programs that are sending millions of dollars toward these efforts for both commercial and passenger vehicle use,” he said.

The U.S. Department of Energy announced $59 million in grants for advanced transportation research projects on August 16, including $7 million for General Motors Co. to develop a low-mass, high-efficiency engine for midsize trucks.

The California Air Resources Board offers matching funds to numerous truck maker efforts to reduce emissions. It announced $205 million in matching grants for clean freight transportation in September 2018.

Upcoming FreightWaves Events
Compliance

Brokerage Compliance Symposium

The day before F3. Every compliance issue you face - fraud exposure, carrier liability, FMCSA rules, cargo theft, insurance gaps - navigated by attorneys and operators defining best practices in a changing industry.

October 26, 2026
The Signal at Chattanooga Choo Choo • Chattanooga, TN
Register Now
Awards

F3 Awards Dinner

The night before F3. FreightTech100 companies honored. FreightTech 25 and Shipper of Choice winners revealed live. Cocktail reception into dinner and live music - 300 industry leaders in one purpose-built room.

October 26, 2026
The Signal at Chattanooga Choo Choo • Chattanooga, TN
Register Now
FreightTech

F3: Future of Freight Festival

Industry-defining keynotes, rapid-fire technology demos, and industry leaders networking in experiences across Chattanooga - plus the inaugural F3 Awards Dinner featuring the FreightTech and Shipper of Choice reveals.

October 27, 2026 – October 28, 2026
The Signal at Chattanooga Choo Choo • Chattanooga, TN
Register Now
Compliance Brokerage Compliance Symposium Oct 26 • The Signal at Chattanooga Choo Choo • Chattanooga, TN

The day before F3. Every compliance issue you face - fraud exposure, carrier liability, FMCSA rules, cargo theft, insurance gaps - navigated by attorneys and operators defining best practices in a changing industry.

The Signal at Chattanooga Choo Choo • Chattanooga, TN Register Now
Awards F3 Awards Dinner Oct 26 • The Signal at Chattanooga Choo Choo • Chattanooga, TN

The night before F3. FreightTech100 companies honored. FreightTech 25 and Shipper of Choice winners revealed live. Cocktail reception into dinner and live music - 300 industry leaders in one purpose-built room.

The Signal at Chattanooga Choo Choo • Chattanooga, TN Register Now
FreightTech F3: Future of Freight Festival Oct 27 – Oct 28 • The Signal at Chattanooga Choo Choo • Chattanooga, TN

Industry-defining keynotes, rapid-fire technology demos, and industry leaders networking in experiences across Chattanooga - plus the inaugural F3 Awards Dinner featuring the FreightTech and Shipper of Choice reveals.

The Signal at Chattanooga Choo Choo • Chattanooga, TN Register Now

Alan Adler

Alan Adler is an award-winning journalist who worked for The Associated Press and the Detroit Free Press. He also spent two decades in domestic and international media relations and executive communications with General Motors.