ACT 2026: Uncertainty still exists over EPA 2027 NOx limit

May 5, 2026

Chris Clonts

The ACT Expo opened with uncertainty still about whether the EPA 2027 NOx regulations would change. One panel predicted they would not. (Chris Clonts)

Though the U.S. EPA has rolled back many emissions regulations surrounding the mobility industry, its HD rules remain intact, meaning manufacturers must hit the world’s most stringent NOx requirement.

It was clear at a panel of industry experts that the new rule was still causing confusion among operators and fleet owners. The EPA’s new limits are set at 0.035 grams per horsepower-hour during normal operation, 0.050 grams at low load and 10.0 grams at idle. A panel immediately following revealed how companies have hit the tough target, which goes into effect in January of 2027.

Andrea Lukas, Cummins director of product management for North American On-Highway Business, said it was important for fleets to understand. She said limits have been flat on particulate emissions and NOx for 10 years, and “this is the big change. So we’re coming into 2027 and it is driving change in the industry.”

Andrea Lukas used this graphic to show how flat particulate and NOx admissions had been for a decade before EPA 2027. (Chris Clonts)

She said that despite the confusion on whether the 35-mg standard would be reduced or eliminated as have other limits, it looked like it would not be changed. “We’ve heard from high-level officials at EPA that that’s sticking, so we need to prepare for that,” she said, adding that there could be changes to warranty requirements (because the new limit would increase the service life of emissions equipment). “Any change to that would be impactful from a cost perspective,” she said.

David Hillman, vice president of integrated technology sales for International, said uncertainty about the rule was holding up definitive pricing for 2027. “What we don't want to do is price given the regulations on the books right now and then have an NPRM [notice of proposed rulemaking] come out that dramatically changes that and then everyone has to pivot,” he said. “So I think from a pricing standpoint, that's the the big pent up question that's on most people's minds in the fleets that I speak to.”

Hillman and Lukas agreed that outside of hitting the new limit, manufacturers are in an arms race to reduce the total cost of ownership.

Their assessment was that, in general, the industry was relatively prepared for the new NOx limit. “The S13 [powertrain] product that we produce ourselves was the result of a seven or eight year product development program that launched in '23,” Hillman said. “So by the time the new regs hit, we'll have been in production for three years, and 90% of that hardware carries over. So I think that helps give us some confidence.”

The two agreed that even with having to hit the new metric, there was an arms race developing between manufacturers to continuously reduce the total cost of ownership.

Patrick Couch, senior vice president, technical, TRC Companies | Clean Transportation Solutions, moderated the panel on EPA 2027. (Chris Clonts)

That confidence was represented across manufacturers at a panel that focused on the current state of clean diesel technology.

Engineers from various manufactures largely agreed with each other on the clean diesel panel: Though hitting the new NOx limit was tough, it was possible to do it predominately with existing technology.

Mehdi Ferhan, head of powertrain technology for Volvo, said the company landed on current technology while insisting on meeting the new emission requirement while maintaining the brand’s high reliability using its current emission treatment system. “We decided… not to reinvent a new technology for EPA 2027 and to build from the current foundation in order to build more durable and uptime-oriented solutions,” he said.

Navtej Singh, director of engineering at International and an SAE fellow, said the company’s new S13 engine retains 94% of the parts of the previous version. “We have already accumulated more than 10 million miles with those drive cycles,” he said. “And there’s no active regeneration, no external EGR. We’re making it so simplified.”

Most of the manufacturers are meeting the new standard by addressing the low temperature of the catalyst during the first five minutes of idol. Grid heaters, modifying combustion settings and fuel injection rates and adjusting aftertreatment were all part of the ultimate solution.

Singh said International worked to minimize any changes in maintenance burden for the customer.

“I think the key thing here is total cost of ownership,” he said. “We made sure that going into 2027, our service intervals are improving, they're not going backward. We also made sure that we are not adding an extra cost on our powertrain systems, like not adding a burden on the folks. [One key element of our powertrain] was the transmission piece, you know? So we kind of like brought in-house T14 transmission, which kind of like, as he mentioned, like help us doing a down. [Reducing overall engine rpm at cruising speed.] It helped us give fuel economy back to the customers.”

Singh also said International was going into the prognostics business, as “it helps us give some fuel economy back to the customers. And we are also trying to go into the prognostics. And in one iteration.”

And prognostics means that if the customer is about to have a fault code or you're about to have other failures, the dealers will be notified ahead of it.

Lyle Locher, director of technical programs and planning in R&T at Cummins, downplayed the challenge the company faced. “Even though it's a big change in NOx reduction, I would say for the most part for us, it's really a no story when it comes to maintenance or additional uptime, things that fleets need to consider.”

Singh agreed about downstream effects on dealers and customers. “I think, for the international dealers and for the customers, I think adoption to 2027 is going to be very easy, very simple,” he said.