There looks to be a shift away from spec’ing 14L engines in new Class 8 trucks in favor of powerplants that range from over 10L to under 14L in displacement. And the trend to smaller-displacement engine is expected to continue as diesel’s market hegemony comes “under attack” by alternative power.
Class 8 Engines: Is Smaller Displacement the Wave of the Future?
There looks to be a shift away from spec'ing 14L engines in new Class 8 trucks in favor of powerplants that range from over 10L to under 14L in displacement, according to ACT Research and Rhein Associates.

An example of a less than 14L and over 10L engine is the 12.8L Detroit DD13.
Photo: Detroit Diesel Corp.
That analysis is included in the N.A. Commercial Vehicle On-Highway Engine Outlookreport recentlypublished by ACT Research and Rhein Associates, which predicts that engines over 10L will account for more than 85% of the Class 8 production between 2020 and 2024.
“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 for Class 8 trucks and tractors, with an acceleration prompted by new emission regulations expected in 2024,” said Tom Rhein, president of Rhein Associates.
For Class 5-7, he said, "the current metric of interest is gasoline penetration, which continues to see share gains.”
Kenny Vieth, ACT president and senior analyst, noted that, “Diesel power is under attack long-term for use in on-highway commercial vehicles. Alternative power is being developed, tested, and refined, even as diesel engines are transitioning to become more fuel-efficient and clean.
“Emission regulations are one of the main drivers of alternative fuel adoption, which is why the Engine Outlook includes a section on the commercial vehicle regulatory environment,” he continued.
Vieth also offered a caution. “While many think this is a California-only phenomenon, we would note that Oregon’s legislators recently voted in favor of a bill to regulate diesel trucks in the Portland metro area, and we continue to see reports about various 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.”
The engine report highlights power-source activity for Class 5 to 8 trucks and includes five-year forecasts of engines volumes and product trends. Rhein Associates is a supplier of powertrain information to worldwide clients. ACT Research is a publisher of commercial vehicle truck, trailer, and bus industry data, market analysis and forecasts for the North America and China markets.
More Fuel Smarts

Volvo Testing Hydrogen-Fueled Internal Combustion Engines on Trucks in Europe
Hydrogen combustion engine trucks will be especially suitable over longer distances and in regions where there is limited charging infrastructure or time for recharging of battery-electric trucks, according to the company.
Read More →
Toyota’s Entry Into Cellcentric Signals Push to Accelerate Hydrogen Truck Adoption
By joining Daimler Truck and Volvo, Toyota brings fuel cell expertise to a joint effort aimed at making hydrogen viable for heavy-duty transport.
Read More →
U.S. Diesel Prices Hit $5.40, Top $7 in California
Trucking operators are slowing speeds, cutting empty miles, and declining unprofitable freight as diesel costs continue to rise due to conflict in the Middle East.
Read More →
EPA Targets DEF Sensor Failures Behind Truck Derates
New guidance allows engine makers to replace problematic DEF sensors with NOx-based systems, aiming to reduce unnecessary derates and downtime caused by failures in the sensors designed to monitor diesel exhaust fluid on trucks.
Read More →
Heavy Duty Trucking is Searching for the Top Green Fleets of 2026
Is your company a leader in sustainability efforts among trucking fleets? If so, Heavy Duty Trucking's editors want to hear from you.
Read More →
What's Real in Advanced Truck Technology? ACT Expo's Erik Neandross Weighs In
Artificial intelligence, the software-defined vehicle, telematics, autonomous trucks, electric trucks and alternative fuels, and more in this HDT Talks Trucking interview
Read More →
Why Diesel Is Climbing Fast—and What the Iran Conflict Has to Do With It
With global oil flows disrupted, U.S. diesel prices have topped $5 across every region, climbing sharply in the past few weeks.
Read More →
From Diesel Prices to Cyberattacks: How the Iran War Is Affecting Trucking
The impact of the Iran conflict extends beyond fuel costs, bringing more fraud and cybersecurity risks to the trucking industry.
Read More →
Vanair Introduces Solar, Battery Power Ecosystem for Class 8 Trucks
The company’s expanded EPEQ ecosystem includes flexible solar panels, lithium batteries, hydraulic power systems, and a portable fast charger for electric trucks.
Read More →
Run on Less “Messy Middle” Data Shows Multiple Paths for Truck Powertrains [Listen]
Listen as Mike Roeth of the North American Council for Freight Efficiency shares insights into battery-electric trucks, natural gas, biofuels, and clean diesel on this episode of HDT Talks Trucking.
Read More →
