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Cummins to phase in 2027 engines due to EPA NOx rule
Manufacturer staggers X15, X10 introduction after reviewing fine print
Cummins unveiled its 2027 EPA-compliant engine at the Technology & Maintenance Council's annual meeting in March. (Seth Clevenger/Transport Topics)
Key Takeaways:
- Cummins plans limited production of its model-year 2027 X15 and X10 engines beginning in January.
- The OEM will continue offering current-generation engines during the transition to newer models.
- Cummins said production plans could change depending on differences between the EPA proposal and the final rule.
Cummins plans to stagger the introduction of two model-year 2027 engines that meet tighter emissions standards after reviewing draft Environmental Protection Agency regulations announced July 9, the manufacturer said July 23, and keep producing the existing versions.
Columbus, Ind.-based Cummins’ plans to phase in proposals long in the gestation are the first domino to drop after details were unveiled for nitrogen oxide emissions regulations, although Volvo Group CEO Martin Lundstedt on July 17 already warned that the lens on second-half 2026 truck sales had been fogged up by the rulemaking.
Cummins will continue manufacturing existing versions of the X15 and X10 engines many truck makers offer for larger trucks and tractors after analyzing the draft notice of proposed rulemaking (NPRM) on changes to NOx tailpipe emissions, the company said.
“Our long-term product strategy has not changed,” CEO Jennifer Rumsey said. “This is about improving the transition, not changing the destination. A phased production ramp will allow us to support customers while building confidence in our new products through real-world operation and maintaining our focus on quality.”
Rumsey attended the unveiling of the NPRM on the National Mall on July 9. Rumsey joined Daimler Truck North America CEO John O’Leary and Paccar CEO Preston Feight on the podium alongside EPA Administrator Lee Zeldin for the launch.
The NPRM kept a Biden-era requirement that NOx emissions for heavy-duty trucks fall to 35 milligrams per horsepower-hour from 200 mg/hp-hr, but manufacturers were offered wiggle room on implementation, noncompliance and NOx credits.
Image
From left: ATA President Chris Spear joined Cummins CEO Jennifer Rumsey, Paccar CEO Preston Feight and Daimler Trucks North America CEO John O'Leary on the National Mall on July 9. (American Trucking Associations)
In the other headline revision, warranties for heavy-duty truck emissions mitigation equipment will be 100,000 miles or five years rather than 450,000 miles or 10 years under the existing rule. That decision is expected to cut the price increase for model-year 2027 trucks by as much as $10,000.
Production plans
Cummins, meanwhile, plans to begin limited production of its model-year 2027 X15 engine in January, based on individual OEM launch plans. Production will ramp steadily, the company said, with full production expected to begin in the fourth quarter of 2027.
However, as part of the revisions to its plans, Cummins expects its current-generation X15 engine to remain available.
Similarly, Cummins expects to begin limited production of the model-year 2027 X10 engine in January, with full production expected by the third quarter, subject to OEM launch plans.
During the transition, the current X12 and L9 engines used in truck and transit bus applications are set to remain available.
That said, Cummins warned that these may not be the last changes. The company expects to continue monitoring development of the final rule — the draft rule included at least one big surprise for truck and engine manufacturers — and product plans and timing could be adjusted if the final rule differs materially from the July 9 NPRM.
Truck makers and Cummins had waited as long as possible to introduce their EPA 2027-compliant engines, with the 2027 X15 not making its public debut until late March at the Technology & Maintenance Council annual meeting.
Cummins already delayed the launch once in August 2025, citing uncertainty around the introduction of the federal tailpipe regulations.
An EPA 2027-compliant X15 comes with a redesigned, larger selective catalytic reduction system and a dedicated 48-volt alternator for two heaters. There is one heater before the diesel oxidation catalyst/diesel particulate filter and one before the SCR segment.
DTNA to offer 6 compliant engines
The diesel X15 is one of six EPA 2027-compliant engines Freightliner and Western Star will offer. Kenworth’s C580 heavy-haul tractor and truck — which was unveiled in March — will come with the X15 as standard.
Cummins, meanwhile, has high hopes for the X10, which was launched in March 2025. It replaces the L9 and X12 engines in Cummins’ North America portfolio and is intended to drive an increase in the company’s heavy-duty truck engine marketplace.
“The X10 definitely opens up another market,” Brett Merritt, president of Cummins’ engine business, told analysts and investors during the 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.
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 said during the May 21 analyst day that the Granite was the first heavy-duty application for the X10.
