Natural gas lineup gives fleets more options to cut costs

Fleets that are already using natural gas trucks stand to gain additional value by expanding with Cummins’ portfolio of natural gas engines. When it comes to medium- and heavy-duty natural gas vehicles, the bigger the fleet, the bigger the savings over a higher-priced, conventional fuel like diesel.

The company’s lineup includes the L9N for medium-duty applications and the X15N for heavy-duty operations, giving fleets flexible options to lower fuel costs and emissions. The X15N is currently the lowest emission heavy-duty engine on the market, producing 75% less NOx than required by the EPA.

According to the U.S. Department of Energy (DOE), cleaner exhaust can simplify emissions control systems and reduce associated costs. Diesel powertrains use proven technologies such as diesel particulate filters (DPF), selective catalytic reduction (SCR) and diesel exhaust fluid (DEF) to meet stringent emissions standards. Natural gas engines achieve comparable emissions performance through a different approach that does not require the same aftertreatment systems, offering fleets another effective path to cleaner operation.

The most notable savings come from increased use of natural gas. According to DOE, the average price of diesel in 2024 was $3.76 per gallon. Natural gas averaged $2.91 per diesel gallon equivalent (DGE), which is about 27% less than diesel for the same period. 

“The economics are the more fuel you burn, the more money you save,” said David King, Cummins Product Manager of Natural & Renewable Gas Engines. 

Those savings can prove particularly attractive for fleets that are already using Cummins natural engines like the L9N and the ISX12N. Adding the 15-liter X15N to that clean-burning lineup will extend those savings even further. 

“You’ve made the investment in fueling and now you get everything you can to burn natural gas,” King said. “It may be hard to justify the fueling infrastructure with an L9N only but when you get the X15N, you start burning a lot of fuel and get a return on investment on that fueling station.”

The Transport Project, a national coalition of fleets, vehicle and engine manufacturers with an interest in gaseous fuels, forecasts an attractive payback period for natural gas vehicles (NGVs). Its experts say trucks are the most promising. 

“Due to lower fuel and maintenance costs, NGVs offer an 18- to 24-month payback,” the non-profit reports on its website. “As production increases and fuel tank prices come down, vehicles will become less expensive and enjoy a shorter payback period. The greatest savings are currently being seen in heavy-duty, high mileage fleets.” 

Major fleet ‘over the top’ with new X15N

According to WM, formerly Waste Management, the company operates the largest heavy-duty natural gas truck fleet in North America. Approximately 70% of its fleet in the United States and Canada consists of about 14,000 natural gas vehicles. The company reports positive results after adding the X15N alongside the L9N and ISX12N engines. WM Corporate Fleet Director Marty Tufte said that natural gas use is on the rise at the Texas-based refuse company. 

Last year, the company displaced 110 million gallons of diesel by using mostly renewable natural gas (RNG) at its 225 stations. At an average price of $3.76 per gallon of diesel, which equates to $93.5 million in fuel savings. Those savings are even higher since WM produces its own RNG from its landfill sites. 

Tufte said natural gas consumption continues to grow at the company and is on track to displacing ten million more gallons of diesel each year. By 2026, WM expects to use only RNG to fuel its natural gas trucks. 

“The one thing that put us over the top is the X15N,” Tufte said. “We are using it in transfer. We're using it in industrial for roll off. We’re pulling doubles.” 

The power of the X15N, which is on par with diesel, has impressed both fleet managers and drivers alike.  

“We just started in Oklahoma City running to Tulsa and there are stretches of the freeway that are 80 miles an hour,” Tufte said. “We speed limit ours at 75. But that engine is running strong with 80,000 pounds all day long.” 

For WM and other fleets with demanding duty cycles it is hard not to appreciate the diesel-like power and increased efficiency of the X15N which offers up to 500 horsepower and 1,850 lb.-ft. torque. Fuel economy is improved up to 10% over the ISX12N while weight is down 50 pounds.  

The case for natural gas powertrains is further strengthened by more predictable pricing and stable fuel supplies in the face of natural disasters and geopolitical headwinds. That is something Tufte has tracked for the nearly three decades that WM has used natural gas trucks. 

“I can show you PowerPoint after PowerPoint where natural gas has been stable for 30 years,” Tufte said. 

The success of WM’s growing natural gas fleet shows that clean, efficient and powerful engines like the X15N and L9N are more than a sustainable choice—they are central to the value proposition, enabling fleets to maximize fuel savings, optimize performance across diverse applications, and achieve a stronger return on investment.