NHTSA Drops Engine-Level Fuel Standards, Shifts to Whole-Vehicle Targets

Will this lower the price of a new Class 8 tractor?

NHTSA announced Friday it will no longer regulate the fuel efficiency of standalone truck engines, transmissions, or tires. The agency says manufacturers should have freedom to decide how a complete vehicle meets federal efficiency requirements, whether through engine improvements, aerodynamics, cab design, or tire selection. NHTSA Administrator Jonathan Morrison said the change will lower commercial truck prices and benefit U.S. manufacturers, but the agency did not provide an estimate of how much the regulatory shift could reduce the cost of new trucks.

The action does not eliminate federal fuel-efficiency requirements for commercial trucks. It reinterprets the Energy Independence and Security Act of 2007 to limit NHTSA's authority to regulating complete medium- and heavy-duty vehicles rather than their individual components. The agency cited the Supreme Court's 2024 Loper Bright decision, which ended judicial deference to federal agencies' interpretations of ambiguous statutes, and a recent D.C. Circuit ruling that NHTSA says found it lacks authority to regulate the fuel efficiency of nonvehicle components.

What were the Obama-era engine standards?

The Phase 2 greenhouse gas and fuel-efficiency standards, finalized jointly by NHTSA and EPA in 2016, established requirements for combination tractors, trailers, heavy-duty pickups and vans, vocational vehicles, and certain engines powering tractors and vocational trucks. The standards were designed to reduce fuel consumption and greenhouse gas emissions through model year 2027. When fully phased in, regulators projected tractors could achieve up to 25 percent lower fuel consumption and carbon dioxide emissions compared with equivalent 2018 tractors.

Federal regulators estimated the program would save truck owners approximately $170 billion in fuel costs over the life of the regulations. They also projected that buyers of new long-haul trucks in 2027 could recover the additional investment in fuel-saving technology in less than two years through lower fuel costs. EPA and NHTSA estimated the broader Phase 2 program would reduce CO₂ emissions by roughly 1.1 billion metric tons over the lifetime of covered vehicles.

The rules were intended to accelerate adoption of technologies ranging from more efficient engines and powertrains to aerodynamic equipment and lighter-weight components. Engine-specific standards were designed to push deployment of technologies that reduce diesel consumption and greenhouse-gas emissions at the component level.

How did manufacturers react to the 2016 rule?

Industry reaction to the final 2016 rule was generally positive, although fleets and manufacturers emphasized the importance of keeping compliance costs manageable and allowing enough time to develop and deploy new technologies. American Trucking Associations officials were cautiously optimistic when the standards were finalized. ATA said it was pleased regulators had addressed concerns over technology-development lead times and flexibility, while warning that the program's ultimate success would depend on fleets' willingness to purchase the new technologies.

Daimler Trucks North America supported the Phase 2 goals but said the rules needed to establish long-term targets for the entire vehicle rather than focusing solely on the engine, while providing manufacturers and customers enough flexibility to determine economically feasible ways of reaching the targets. Paccar said it would meet the standards while delivering fuel-efficient Kenworth and Peterbilt trucks. Volvo Group North America called improved fuel economy a goal stakeholders could unite around but described the targets as a significant challenge for the industry.

What happens to existing Phase 2 standards?

Friday's action does not immediately repeal the existing medium- and heavy-duty standards. NHTSA said the interpretive rule establishes the legal foundation for a forthcoming notice-and-comment rulemaking that would formally reset its medium- and heavy-duty vehicle program. Until that process is completed, the agency said it will exercise its enforcement authority consistent with its new interpretation.

The move concerns NHTSA's fuel-efficiency authority and does not, by itself, eliminate EPA's separate authority under the Clean Air Act to regulate emissions from heavy-duty engines. EPA retains explicit authority over engine emissions, unlike NHTSA's fuel-efficiency mandate under EISA, which the agency now says does not give it explicit authority to regulate engines or components such as transmissions and tires.

What does this mean for TCO?

Removing NHTSA's engine-level requirements could give manufacturers greater flexibility and potentially lower upfront equipment costs, but the effect on long-term fuel consumption and emissions will depend on how the agency structures its vehicle-level standards. The shift could carry trade-offs. If manufacturers choose lower-cost compliance paths that deliver less fuel savings than the component-specific standards would have required, the two-year payback period federal regulators projected for 2027 long-haul trucks could stretch longer or disappear.

The emphasis on manufacturer flexibility echoes concerns raised by the trucking and manufacturing industries when the Phase 2 standards were adopted a decade ago. Whether that flexibility translates into lower purchase prices or simply shifts the compliance burden from component engineering to whole-vehicle optimization remains to be seen. NHTSA has not yet published the vehicle-level standards that will replace the engine-specific targets, so fleets ordering 2028 and later model-year trucks do not yet know what fuel-economy performance to expect or what premium they will pay for it.