Cummins X10 Targets Heavy-Duty Market Share With 70 HP, 400 lb-ft Gain

How much more power does the X10 deliver than the L9?

Cummins' X10 engine adds 70 horsepower and 400 pound-feet of torque over the outgoing L9, moving from a medium-duty big-bore design to a heavy-duty architecture. The X10 launched in March 2025 and replaced both the L9 and X12 in Cummins' North America portfolio. Brett Merritt, president of Cummins' engine business, told analysts May 21 that the X10 opens a new market segment and will drive heavy-duty market share gains.

Cummins offers two X10 ratings: a heavy-duty package rated up to 450 hp and 1,650 pound-feet of torque, and a medium-duty version with up to 380 hp and 1,250 pound-feet. The engine extends oil-drain intervals to 25,000 miles beyond the L9's current spec. For vocational applications, the X10 delivers 590 pound-feet continuous and up to 664 pound-feet intermittent power takeoff capability.

Which OEMs are offering the X10?

Mack Trucks was the first heavy-duty OEM to adopt the X10, adding six power profiles to the revamped Granite vocational truck lineup unveiled in March 2026. Merritt said during the investor day that many of Mack's peers will follow a similar path.

Daimler Truck North America announced in March that Freightliner and Western Star customers will be able to choose the X10 alongside the B6.7 Octane gasoline engine, the X15 diesel, and the Detroit Gen 6 lineup for model year 2027 trucks. Paccar, Cummins' largest customer among truck makers, has not yet announced X10 availability. The L9, branded as the PX-9 in Paccar chassis, was previously available in Kenworth's T180, T280, T380, and T480 trucks plus Peterbilt's Models 536, 537, and 548.

How does the X10 meet 2027 EPA NOx limits?

The X10 uses a 48-volt electrical system to heat emissions-control components and meet the EPA 2027 nitrogen oxide standard. The regulation drops NOx emissions for heavy-duty trucks 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 cited in the source.

Cummins delayed the launch of its EPA 2027-compliant X15 engine in August 2025, citing uncertainty around the introduction of the federal tailpipe regulations. The X15 made its public debut in March 2026 at the annual meeting of American Trucking Associations' Technology & Maintenance Council.

What fuel options will Cummins offer for the X10?

The X10 is part of Cummins' High Efficiency, Lower emissions, Multiple fuels program. Cummins plans to offer non-diesel variants of the X10, similar to the X15N natural gas-fueled engine. Each variant is derived from a base engine with common parts below the head gasket. Components above the head gasket vary based on fuel type. Cummins has not disclosed timing or specific fuel options for X10 variants.

What this means for spec'ing 2027 trucks

The X10 fills the gap between medium-duty and traditional Class 8 power ratings. Fleets running L9-powered vocational trucks gain a direct upgrade path with 70 additional horsepower, 400 pound-feet more torque, and a 25,000-mile longer oil-drain interval. The extended service interval cuts scheduled maintenance stops and labor hours over the truck's life. The 48-volt electrical system for emissions heating adds complexity but is required to meet the 2027 NOx standard, which applies across all heavy-duty diesel engines.

For fleets considering the X10 in 2027 builds, the key unknowns are pricing versus the L9, parts availability in rural markets, and whether the 48-volt system requires new shop tooling or diagnostic equipment. Cummins has not released MSRP, warranty terms, or service-interval details beyond the oil-drain spec. The Volvo D13 engine meets the 2027 EPA NOx standard, but VTNA has similarly withheld fuel economy, service intervals, and pricing.

Mack's adoption of the X10 in the Granite signals vocational-fleet interest, but the engine's success in over-the-road applications depends on Paccar's decision and whether DTNA customers choose the X10 over the Detroit Gen 6. Merritt's market-share forecast hinges on OEMs beyond Mack offering the X10 across multiple truck models, which has not yet materialized in public announcements.