Fleets Grow More Confident About RNG Powertrains
OEMs’ Introduction of X15N Engine Builds On-Highway Support
Key Takeaways:
- J.B. Hunt has 200 compressed natural gas trucks, most of which have 12-liter engines.
- Over the past 12 months, J.B. Hunt has introduced 15-liter RNG engines to its fleet.
- The carrier's trucks are fueled 8,000 times a day. and J.B. Hunt buys the equivalent of 200 million gallons a year of diesel.
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SAN DIEGO — Optimism about new technology is typically abundant from truck, engine or aftermarket enhancement manufacturers, less so from the executives tasked with paying for new, often more expensive rolling stock or a safety advance.
But wariness about larger powertrains using renewable natural gas is starting to wane among on-highway carrier ranks, according to a senior executive at one of the largest fleet owners in the U.S.
has 200 compressed natural gas trucks, most of which have 12-liter engines. Over the past 12 months, the carrier introduced 15-liter RNG engines to its fleet. Full production of Cummins’ X15N natural gas engine got underway in September 2024.
“I’m glad to say we’re seeing a positive trend,” said , J.B. Hunt vice president of energy and sustainability. “We are seeing better fuel economy with the 15-liter than the 12-liter by 3% to 5%.”
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J.B, Hunt Transport Services — which ranks No. 3 on the Transport Topics Top 100 list of the largest for-hire carriers in North America, No. 1 on the intermodal sector list and No. 2 in the truckload/dedicated segment — has more than 22,000 trucks overall.
J.B. Hunt trucks are fueled 8,000 times a day. The carrier buys the equivalent of 200 million gallons a year of diesel. But biodiesel, renewable diesel and RNG now account for 22% of J.B. Hunt’s total fuel by volume, said Mounce.
“We’re going to convert hundreds more of these trucks” to RNG, Mounce said at American Trucking Associations’ Management Conference & Exhibition. “We’re in a spot now where we’re a lot closer to cost parity.”
“Over the next couple of years, we’ll see a lot more data points,” said Mounce, while noting that trucks with a natural gas powertrain currently cost 50% more than a diesel peer.
Freightliner opened its order book for fifth-generation Cascadia tractors powered by the X15N on the opening day of the 2025 Advanced Clean Transportation Expo in Anaheim, Calif., in April, providing a focal point for a show floor abuzz with talk of a surge in demand for RNG-powered trucks.
The Cascadia, the best-selling Class 8 tractor in the U.S., received an overhaul in 2024.
X15Ns already were available for Kenworth’s T680 and T880 models and Peterbilt’s 579 semi, 567 vocational and 520 refuse models.
David King’s 36-year journey at Cummins—from a curious engineering student to leading the X15N natural gas engine—embodies passion, purpose, and progress. His work is helping drive a cleaner, more sustainable future for the trucking industry.
Thank you, David, for inspiring us… — Cummins Inc. (@Cummins)
Cummins argues the X15N matches the performance of its biggest diesel engine, unlike its predecessors. The X15N is available with as much as 500 horsepower and 1,850 pound-feet of torque.
The X15N has a broader torque range than a 12-liter engine, as well as offering more low-end torque, Mike Barr, Cummins’ director of on-highway sales for the western U.S., told MCE attendees.
We don’t just talk about sustainability – we produce and deliver it, one gallon of at a time.
Take a look at our 2024 – packed with milestones that reflect our commitment to : — Clean Energy (@ce_renewables)
Clean Energy Fuels showcased a 2026 Cascadia day cab powered by an X15N engine at MCE. The fuel provider also has an X15N-powered Peterbilt demonstrator truck.
And Clean Energy recently signed deals with Wisconsin-based Paper Transport, USA Hauling & Recycling, Republic Services and United Dairymen of Arizona. Paper Transport ranks No. 97 on the TT for-hire Top 100.
Production of RNG — either at waste landfill or anaerobic digestion facilities — also is growing.
Opal Fuels began commercial operations at its 12th production facility in Egg Harbor Township, N.J., at the start of October. The landfill waste facility is a partnership with South Jersey Industries and the Atlantic County Utilities Authority.
The fueling network is “night and day” compared with 10 years ago for natural gas, said Mounce, a factor that eradicates many of the hurdles that battery-electric trucks face.
“This year, we’ve got a lot of new people dipping their toe in the water,” said Eric Bippus, a fellow panelist and Hexagon Agility chief commercial officer. “There’s a whole host of people out there with fueling solutions.”
Natural gas vehicles consumed the equivalent of 774 million gallons of gasoline in the U.S. in 2024, according to figures released by The Transport Project at the end of June.
Some 86% of natural gas vehicles were fueled by RNG last year, the advocacy group’s data show, even though the U.S. was the largest producer of conventional natural gas in the world in 2024.
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