Uncertainty raises questions about 2027 diesel specs

While there are more questions than answers about how 2027-model diesel engines will be set up, it appears that relaxed federal exhaust emission regulations will mean current models will continue for some time.

The Trump administration’s Environmental Protection Agency has already loosened the rules regarding diesel exhaust fluid, and appears poised to cut back on stricter limits for nitrogen oxides, soot and greenhouse gas, and reduce the requirements for longer warranties.

Modified rules could mean diesels produced as of Jan. 1, 2027, will not need specialized hardware and software that engine builders have been developing to meet the ’27 limits published in ’23. That probably won’t forestall price increases needed to pay for many millions of dollars in development costs borne by original equipment manufacturers, though any changes on that score will likely be masked by price hikes from normal inflation and Trump’s tariffs.

“Cost of the 2027 emissions rules is anyone’s guess – we’ve all seen the statements of $20,000 or more,” said Allen Schaefer, executive director of the Engine Technology Forum. “I know warranty costs are big on the minds of the OEMs for these systems. They have now a decade-plus of experience seeing where the failures and costs are incurred, and getting 50% NOx reduction over what is already near zero and sustaining it for 650,000 miles is significant.”

That 650,000 miles is a period during which exhaust-emission equipment on 2027 heavy-duty diesels must be kept functioning, but the EPA is expected to cut that to the current 450,000 miles. That would please manufacturers but upset truck buyers if they must still purchase ’27-spec diesels with expensive new equipment, Schaefer noted. Operators expect payback on higher costs through better fuel economy, greater durability and longer life, which do not seem guaranteed.

As the regs now stand, the ’27 diesels must cut NOx by 82.5% and particulates by 50% compared to current models, which are considered very clean. To achieve this, ’27 Cummins diesels will have, among other things, electric heating grids to keep exhaust-aftertreatment systems at proper operating temperatures. Cummins has said its grids will be powered by a separate 48-volt alternator driven by the engine. Other engine makers will use similar approaches.

“We’re seeing legal challenges to the EPA’s actions on greenhouse gases, we are still waiting to see how they will approach NOx, and they’ll probably get challenged on that, too, whatever they do,” said Kevin Grove, director, safety and technology policy at the American Trucking Associations. “OEMs are probably continuing their existing plans while waiting to see how things play out.”

Manufacturers are quiet about what they intend to do amid turbulence in Washington and won’t know until regulatory decisions are finalized. If you’re driving a late-model truck, what you see under its hood is likely what will be there in trucks assembled well into 2027. Maybe. LL