On January 1, 2027, Class 7 and Class 8 trucks in the United States begin certifying to 0.035 g/bhp-hr of nitrogen oxides. The final text of the rule that sets that number is expected in December.
The timing came from Cummins chief executive Jennifer Rumsey on the company’s November 5 third-quarter call: the draft opened in July, comments closed at the end of August, and the agency is working through them. “Our understanding is we will likely see that in December,” she said. The same day, Cummins cut its 2026 North American medium-duty truck forecast to 125,000-130,000 units from 130,000-140,000, attributing part of the gap to customers holding orders while the detail stays open.
From 0.20 to 0.035
The limit itself has not moved: 0.20 g/bhp-hr down to 0.035, an 82.5% cut carried over from the 2022 heavy-duty NOx rule that the EPA said in March 2025 it would re-evaluate. The July 2026 draft kept the number and loosened the path – staggered introduction, revised non-conformance penalties, credit flexibility. The 0.050 g/bhp-hr penalty tier is the hinge of that arrangement. The draft sets a per-engine fee. Whether the final rule keeps it is the question fleet buyers cannot yet answer.
Effective First, Final Later
Lay the dates side by side: July draft, end-August comment close, a September commitment from Daimler Truck North America to meet 0.035 without the penalty option, December final, January 1 effective. A few weeks separate publication from enforcement, and fleets must spec 2027 trucks before they can read the whole rule. That gap already shows up in order books, and the trimmed medium-duty forecast is its price.
Cummins is moving slower than the calendar. Limited output of the X10 and X15 starts in January, full production follows in the third and fourth quarters, and the switch completes in early 2028. Current engines keep selling through the transition, with penalty costs recovered from customers where they apply. The manufacturer bought itself two years of runway; the buyer got weeks.
For trucks already on the road, the timetable lands on residual values. Model year 2026 and older are not bound by 0.035, which lifts demand for late used iron; early 2027 builds may depreciate faster if buyers treat the new aftertreatment as unproven. Their emissions are settled on a different track – inspection, access rules, retrofit – not by how much SCR a new engine carries. The truck exhaust purifiers AIFILTECH builds serve exactly that fleet: trucks the new rule will never cover, which still have to pass a smoke test.
