Environmental Protection Agency Administrator Lee Zeldin on July 9 announced a proposal to eliminate deratements caused by diesel exhaust fluid (DEF) system failures, as well as tweaks to the upcoming 2027 heavy-duty nitrogen oxide (NOx) rule.
Speaking at an event in Washington alongside trucking industry representatives, Zeldin said the savings from the proposal could reach up to $6,000 per vehicle on new truck purchases.

Once formally published in the Federal Register, EPA will accept comments for 45 days and also hold a public hearing before issuing a final rule.
“Americans depend on reliable trucks to move essential goods across the country. If finalized, these changes will help manufacturers keep improving their vehicles without being forced to rush products to market before they’re ready,” said Zeldin. “The Trump EPA is committed to making trucking safe and reliable again while protecting human health and the environment.”
EPA’s proposal leaves in place the NOx emissions limits for model year 2027 trucks that were set in 2023 under the Biden administration. The rule requires heavy-duty vehicles to limit NOx emissions to 0.035 grams per horsepower-hour during regular operations.

However, the updated proposal, if finalized, would make several important changes:
- Warranty: Maintains the current 5-year/100,000-mile warranty, rather than a higher mileage warranty.
- Useful life: Delays the scheduled increase in regulatory useful life by three years, so the 11-year/650,000-mile warranty for heavy-duty trucks will take effect in 2030.
- Production volume allowance: Allows up to 5% of a manufacturer’s U.S.-directed production to meet pre-2027 requirements in 2027-29 without requiring the use of NOx credits as is currently required.
- Nonconformance penalties: Allows manufacturers to sell vehicles that do not meet the .035 mg/hp-hr NOx standard provided they pay a fee based on the level of non-compliance.
- DEF derate: Eliminates the requirement for speed and power inducements and replaces them with visible and/or audible dashboard notifications for new trucks. The engine would operate normally until a repair can be made.
“We appreciate EPA taking our concerns seriously and acting to provide commonsense flexibility for the manufacturers, fleets, and 8.4 million hardworking men and women who keep this country moving,” said Chris Spear, president and CEO of American Trucking Associations.
Spear was joined at the event on the National Mall with the heads of Daimler Truck North America, Paccar, and Cummins. They also praised Zeldin for listening to the industry’s concerns and finding a balance between environmental concerns and business realities.
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