‘Fabulous’ year for Cummins X15N natural gas engine

From tough terrain across the United States for UPS to steep grades in Canada, Cummins’ X15N natural gas engine has spent its first year proving it can handle heavy hauls while delivering near-zero emissions at a lower fuel cost than diesel.

It’s been a year since Cummins launched its X15N natural gas engine and its résumé keeps growing.

With up to 500 horsepower and 1,850 lb.-ft. of torque, the X15N is the trucking industry’s most powerful natural gas engine yet. It continues opening doors to heavy hauls that were previously closed to natural gas.

Released ahead of 2027 emission standards adopted by the Environmental Protection Agency and the California Air Resources Board, the X15N has been meeting those strict regulations while delivering what customers describe as diesel-like performance.

The green profile gets even better for fleets and owner-operators using renewable natural gas (RNG), which has the lowest carbon intensity score of all transportation fuels.

Growing RNG availability has made the X15N an even stronger option for fleets.

"It's been fabulous," Cummins Product Manager of Natural & Renewable Gas Engines David King said recently in a Cummins Power Onward podcast. "We've had people refer to it as a gamechanger for the industry. There's been a lot of excitement. A lot of customers who were natural gas customers with us are adopting but also customers who have never used natural gas are trying it out and moving some of their fleet over."

Customers who have tried an X15N-spec’d truck — available for demo use through fuel suppliers like Clean Energy and Chevron — have been coming back for more.

"What really gets exciting is when we see repeat buys," King continued. "So even within the first year, we've got customers who jumped in line, got trucks, tried them out and now they've re-upped their order. And in some cases we've had a third order from customers. And that's all within one year. It's really exciting."

Clean Energy’s demo program offers Peterbilt and Freightliner tractors equipped with the

Cummins X15N. Some of the nation’s top fleets signed up to try the trucks with fuel supplied by Clean Energy, the nation’s largest supplier of transportation-based RNG.

"There’s been big interest which is a great indicator of carrier and shipper interest in running on clean-burning RNG," said a Clean Energy spokesperson. "Driver feedback has been positive, reporting on its diesel-like performance and the affordability per gallon savings running on RNG.

The positive feedback reinforces our belief that the X15N is a near zero emissions game changer for heavy-duty trucking. With power output up to 500 hp and a 750-mile range on a single fill, it proves that clean, sustainable performance doesn’t have to compromise operational efficiency. We are excited that the momentum around RNG and the X15N continues to grow."

A Not-So-Messy Middle

One of the most revealing events this past year for Cummins X15N was the North American Council for Freight Efficiency (NACFE) Run on Less Messy Middle demonstration.

Messy Middle describes the transition between diesel and zero-emission trucks.

As development of zero-emission trucks and infrastructure continue, a variety of low-emission alternative solutions such as hybrids, renewable diesel and natural gas can help fill the gap.
Trucks used in NACFE’s Run on Less events including Messy Middle are closely monitored for performance in a variety of climates, altitudes and terrain. For 2025, Messy Middle monitored three fleets using Cummins X15N: UPS, Wegmans and Kleysen Group.

UPS, a longtime user of alt fuel technologies including natural gas, spec’d the X15N in a Kenworth T680 for use in its fleet in Salt Lake City, Utah where local air quality has long been below federal standards. The Environmental Protection Agency has designated the area as a non-attainment zone.

UPS has cut emissions in Salt Lake by adopting natural gas vehicles; 92% of its package fleet now runs on RNG along with most of its tractors.

Pairing Cummins X15N with the Kenworth T680 has now allowed UPS to use the truck on challenging mountainous routes.

"I’ve been very happy with this truck," UPS driver Gene Horne told NACFE in a video published on its website. "I heard that they do just as well as the diesels and they do. It’s much quieter being in a CNG than a diesel. It makes a lot less noise. This is my favorite truck that I’ve driven for UPS."

Weather hasn’t been an issue either.

"In the extreme cold, the CNG still starts. They don’t need heaters. They still start unlike diesels. And in the extreme heat of Phoenix, Arizona, they do the same thing. Whether it’s cold or hot, I’ve not had any temperature-related issues on CNG," said Mike Backus, Automotive Director for Maintenance at UPS.

Messy Middle participant Wegmans, a popular grocery chain in the Northeast, used its X15N-equipped Peterbilt to pull doubles up challenging grades in New York. A 140,000 lb. load between two 48-foot trailers tackled the climb with near-zero emissions thanks to the X15N.

"We can now do tandem and that was the biggest key that we were missing. That 15-liter, you know, that extra power is very nice," said Mike Loss, Transportation Operations Manager at Wegmans.

Canada-based Kleysen Group’s first natural gas truck, an X15N-equipped Peterbilt sleeper, proved its worth on steep grades in temperatures ranging well below zero degrees Fahrenheit to the upper 80s.

"When we got our first natural gas truck, we determined that we wanted to operate in some of our harshest environments, which is Northern Alberta from Edmonton Grand Prairie to Fort McMurray in particular," said Phil Rivard, Vice President for Distribution Services at the Kleysen Group.

"There are other fuels but we don't find yet that they have the technologies for Class 8 trucks pulling 63,500 kilos (140,000 lbs.)," Rivard continued.

Well-Earned Praise

Cummins X15N’s impressive performance in NACFE’s 2025 Messy Middle earned praise from longtime engineer and NACFE’s Director of Technologies, Rick Mihelic.

"All the promise seen in 2010 has been refreshed now 15 years later. Fleets that abandoned natural gas-powered Class 8 trucks are starting to reconsider them. Early experience is showing the new engine can run competitively with the diesels," Mihelic wrote in a recent column for Commercial Carrier Journal.

"Fleet testing of early pre-production engines began in 2023. Finally, in 2024, Cummins launched production of the X15N. Natural gas was back in freight news headlines," Mihelic continued.

And it looks like it will stay there for a while as other major fleets like WM (formerly Waste Management), J.B. Hunt, Werner and Ozinga Renewable Energy Logistics continue to give props to the cleanest-running heavy-duty engine of 2025.