NHTSA Ends Truck Engine Efficiency Power
The Trump administration's NHTSA has reinterpreted federal law, stating it lacks authority to set fuel-efficiency rules for standalone truck engines and
The National Highway Traffic Safety Administration (NHTSA) announced on Friday it is rescinding its authority to regulate the fuel efficiency of standalone truck engines and components. This interpretive rule, based on a new reading of federal law, shifts regulatory focus to complete vehicles and gives manufacturers greater freedom in meeting standards.
According to a news release from the White House, NHTSA exceeded its legal authority under a regulatory framework expanded during the Obama administration in 2016. The agency now states its authority is limited to regulating the fuel efficiency of complete medium- and heavy-duty vehicles, not separate components like engines, transmissions, or tires.
"The Trump Administration is getting out of the way so manufacturers can decide how they want to meet fuel efficiency requirements," NHTSA Administrator Jonathan Morrison said in a statement. Morrison claimed aligning the program with this interpretation will lower commercial truck prices and benefit U.S. Manufacturers, though NHTSA provided no cost reduction estimate.
Regulatory Shift Follows Court Rulings
The agency cited the Supreme Court's 2024 Loper Bright Enterprises v. Raimondo decision, which overturned the Chevron doctrine on judicial deference to agencies. NHTSA also pointed to a recent U.S. Court of Appeals for the D.C. Circuit decision it says found the agency lacks authority to regulate nonvehicle components' fuel efficiency.
NHTSA said the Energy Independence and Security Act of 2007 authorizes a fuel-efficiency program for commercial vehicles but, unlike the Clean Air Act governing the EPA, does not explicitly grant authority over engines or components. This action targets regulations developed under Obama as part of an effort to reduce commercial truck fuel consumption and greenhouse gas emissions.
Phase 2 Standards and Industry Reaction
The Obama administration implemented the 2007 mandate starting in 2011, expanding it through Phase 2 greenhouse gas and fuel-efficiency standards finalized jointly by NHTSA and the EPA in 2016. These standards covered combination tractors, trailers, heavy-duty pickups and vans, vocational vehicles, and certain engines, aiming to reduce consumption and emissions through model year 2027.
Federal regulators estimated the program would save truck owners $170 billion in fuel costs over the regulations' lifetime. They projected new long-haul truck buyers in 2027 could recover the technology investment in under two years through lower fuel costs. When fully phased in, regulators projected tractors could achieve up to 25% lower fuel consumption and CO₂ emissions versus equivalent 2018 tractors.
Industry reaction to the 2016 rule was generally positive but emphasized cost and flexibility. American Trucking Associations was "cautiously optimistic," pleased regulators addressed technology-development lead times. Daimler Trucks North America supported the goals but said rules needed long-term targets for the entire vehicle, not just the engine. Paccar said it would meet the standards, and Volvo Group North America called improved fuel economy a unifying goal but a significant challenge.
Implications and Next Steps
The shift could carry trade-offs. Engine-specific standards aimed to accelerate deployment of technologies reducing diesel consumption and greenhouse-gas emissions. EPA and NHTSA estimated the Phase 2 program would save $170 billion in fuel costs and reduce CO₂ emissions by roughly 1.1 billion metric tons over covered vehicles' lifetimes.
Removing NHTSA's engine-level requirements may increase manufacturer flexibility and potentially lower upfront costs, but the effect on long-term fuel consumption and emissions depends on how the agency structures vehicle-level standards. Friday's action does not immediately repeal existing standards. The interpretive rule establishes the legal foundation for a forthcoming notice-and-comment rulemaking to formally reset the medium- and heavy-duty vehicle program.
Until that process completes, NHTSA said it will exercise enforcement authority consistent with its new interpretation. The move concerns NHTSA's fuel-efficiency authority and does not eliminate EPA's separate authority under the Clean Air Act to regulate emissions from heavy-duty engines.
