Cummins Expects X10 to Lift Heavy-Duty Truck Engine Share

“You will see market share growth in heavy duty via the X10,” Merritt says. (Cummins)

Cummins executives expect an increase in the company’s heavy-duty truck engine market share in the United States, citing increased competencies in the space due to the introduction of the X10 platform.

Launched in March 2025, the X10 replaced the L9 and X12 engines in Cummins’ North America portfolio. The X10 joined the X15 engine among Cummins’ options for heavy-duty trucks and tractors.

“The X10 definitely opens up another market,” Brett Merritt, president of Cummins’ engine business, told analysts and investors during the Columbus, Ind.-based company’s 2026 investor day. “You will see market share growth in heavy duty via the X10.”

While the L9 was seen as a versatile option in the medium-duty market, Cummins is pitching the X10 as a candidate for those fleets and for customers with heavy-duty needs.

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Merritt 

“The X10 moves from a legacy big bore design to a true heavy-duty architecture. In layman’s terms, this adds 70 additional horsepower [and] 400 pound-feet of torque, and it improves our oil drain interval 25,000 miles versus the current L9,” Merritt said.

Cummins is offering two X10 ratings: a heavy-duty option of up to 450 hp and 1,650 pound-feet of torque and a medium-duty package with up to 380 hp and 1,250 pound-feet of torque.

To be more attractive to vocational truck customers, the X10 offers 590 pound-feet continuous and up to 664 pound-feet intermittent of power takeoff capability.

The engine is compliant with Environmental Protection Agency 2027 nitrogen oxide emissions requirements, using a 48-volt electrical system to heat emissions-control components.

EPA is set to leave in place a Biden-era requirement that NOx emissions for heavy-duty trucks drop to 35 milligrams per horsepower-hour from 200 mg/hp-hr. The agency is expected to publish a notice of proposed rulemaking by late June, according to truck and engine makers.

Cummins delayed the launch of its EPA 2027-compliant X15 engine in August 2025, citing uncertainty around the introduction of the federal tailpipe regulations.

But the engine made its public debut in March at the annual meeting of American Trucking Associations’ Technology & Maintenance Council.

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Cummins displays the X15 in a tractor at 2026 TMC. (Seth Clevenger/Transport Topics)

Earlier in March, Mack Trucks unveiled a revamp of its Class 8 Granite vocational truck. The X10 is available in six power profiles for the Granite.

Merritt told investors during the May 21 analyst day that the Granite was the first heavy-duty application for the X10, expressing excitement at the option being offered by the Volvo Group division. The executive added, however, that many of Mack’s peers would follow a similar path with the X10.

Daimler Truck North America said in March that Freightliner and Western Star customers will be able to choose from six Cummins engines for model year 2027 trucks.

DTNA said customers will be able to choose Cummins’ B6.7 Octane gasoline engine plus the X10 and X15 diesel engines alongside the Detroit Gen 6 lineup launched in February.

Meanwhile, as Cummins CEO Jennifer Rumsey noted during the analyst day, Paccar is Cummins’ largest customer among truck makers.

The L9, which was branded as the PX-9, was available as an option for Kenworth’s T180, T280, T380 and T480 trucks plus Peterbilt’s Models 536, 537 and 548.

The X10 is part of Cummins’ High Efficiency, Lower emissions, Multiple fuels program. The engine maker is set to offer non-diesel options of the X10 as it already does with the X15N natural gas-fueled engine.

Each is derived from a base engine, which means they have some common parts. Below the head gasket, the engine variants have similar components, but above the head gasket, components vary based on fuel type.