Clean Energy Peterbilt 579 day cab demo truck equipped with Cummins X15N natural gas engine
High praise results are in for new, big-load engine
On the path to revolutionize the heavy-duty trucking industry, Cummins’ new 15-liter natural gas engine, the X15N, is attracting attention from some of the country’s most important carriers and fleets as the next game-changing solution that will help long-haul, Class 8 trucks effectively reduce emissions easily and affordably.
In a market where a viable, fit for purpose low-emissions option for longer-range applications currently does not exist, the new X15N powered by renewable natural gas (RNG), is gaining traction as a frontrunner putting heavy-duty carriers at ease. Designed to run on clean RNG, a biofuel derived from organic waste such as cow manure, trucking fleets running routes powered by RNG can reduce emissions by over 300 percent versus conventional diesel.
Through leasing demo models and partnering with OEMs, the country’s top fleets are currently engaged in challenging the X15N’s capabilities while fueling with RNG. The results are in – the engine is quickly earning its stripes and reputation for performance and sustainability that could reshape the future of heavy-duty trucking.
The Cummins X15N: A new era in decarbonization
Cummins 15-liter X15N natural gas engine
Cummins, known for its high-performance engines, introduced the X15N (which will be commercially available in 2025) with a distinct purpose – to deliver powerful, reliable and cleaner transportation. The X15N engine not only reduces greenhouse gas emissions significantly but also offers a solution for fleets looking to transition to a lower-carbon fuel without sacrificing performance.
RNG is particularly promising as it can achieve carbon-neutral or carbon-negative emissions, depending on its source. By integrating RNG into transportation operations, the benefits are three-fold – carriers can make meaningful strides toward achieving sustainability goals, pass emissions reductions down to their customers, all while addressing both environmental concerns and regulatory pressures in tandem, all at a cost that can be significantly lower than diesel.
Real-world testing
Cummins has strategically rolled out the X15N engine for extensive testing, partnering with several fuel providers and fleets nationwide. The X15N is currently being tested by the likes of Walmart, Amazon, UPS, Werner, Knight Swift, Food Express and Mullen Group, to name a few, and reviews are enthusiastic.
Clean Energy, the largest provider of RNG for transportation in North America, has taken a prominent role in showcasing the X15N engine’s capabilities. The company launched a demo truck program in September with a 2025 Peterbilt 579 day cab tractor equipped with the X15N available for fleets to run in two-week intervals utilizing Clean Energy’s 600-strong RNG fueling locations. Up first was J.B. Hunt, one of the largest commercial fleet operators in the country.
Fleets seal of approval
As various X15N test engines continue doing rounds, the testimonials have poured in from drivers and carriers who’ve had the chance to run the engine.
J.B Hunt kick off Clean Energy’s X15N demo program
Following J.B. Hunt’s two-week trial with Clean Energy’s X15N demo truck, they praised the engine’s smooth handling and efficiency. J.B. Hunt has committed to expanding the use of biogenic fuels to reach its goal to reduce carbon emission intensity by 2034 – and RNG paired with the X15N is helping them do just that. A J.B. Hunt driver commented: “I can tell you right now it has a lot more torque than its predecessor [the 12L], I can just feel that on the flat surface so I can just imagine what it can do once we start going up the hills.”
Ruan trial Clean Energy’s demo truck equipped with the X15N for a two-week test period
Ruan Transportation was next to complete their two-week trial running Clean Energy’s demo and were able to experience the engine’s impressive capabilities and emissions reductions fueling with RNG: “We have operated more than 160 CNG trucks that have logged 80 million miles on RNG derived from cattle manure. The RNG has resulted in GHG reductions of over 70,000 metric tons and millions of pounds of CO2 emissions reductions.”
Knight Swift refueling at Clean Energy’s Port of Long Beach RNG station
Dave Williams, Knight-Swift Transportation’s Senior Vice President of Equipment and Government Relations said: “We must ensure we are utilizing the most reliable and efficient technologies possible that help us reduce our carbon footprint. We value our collaboration with Cummins and are encouraged by what we have seen so far with the 15L RNG technology.”
Another early tester of the X15N engine, Food Express President, Kevin Keeney adds: “The addition of the new truck with Cummins’ latest clean technology into our fleet falls nicely into our decarbonization plans. Having the power and torque of a larger engine is ideal for many of our routes, and it is an added benefit for it to operate with an ultra-low carbon fuel like RNG.”
In Werner’s Sustainability Report released in November 2024, it states: “The introduction of the Cummins 15-liter engine—which we are currently testing—has shown promise in overcoming [its predecessors’] hurdles. We’re using RNG in this truck, which significantly reduces emissions.”
The energy transition has been evolving for many years, and thus far, few if any other technologies have proven to give heavy-duty truck operators everything they need – reliability and performance of the vehicle, an existing fueling infrastructure, and emissions reductions for themselves and their customers, all at a cost that keeps them competitive. Today, tens of thousands of city buses and sanitation trucks check those boxes every day operating on RNG with a Cummins natural gas engine. With the introduction of the X15N, the heavy-duty truck market can join the club.