USDOT to reverse fuel economy standards for heavy-duty commercial vehicle engine makers
Federal authorities announced new rulemaking to reverse certain restrictions on commercial truck fuel efficiency standards for engine manufacturers.
On August 28, 2026, the U.S. Department of Transportation’s (USDOT) National Highway Traffic Safety Administration (NHTSA) debuted a new interpretive rule to reverse an Obama-era regulation related to standalone medium- and heavy-duty truck engine fuel efficiency.
“The rule – which went far beyond Congress’ intent – restricted manufacturers’ ability to design innovative approaches to meet commercial truck fuel efficiency standards. Under the Trump Administration, NHTSA is returning that authority to vehicle manufacturers who can best decide how to improve fuel efficiency,” the agency said in a news release.
The rule reconsiders the scope of NHTSA’s authority to set fuel economy standards for standalone commercial vehicle engines.
Officials say that the Energy Independence and Security Act of 2007 (EISA) “requires NHTSA to set fuel economy standards for medium- and heavy-duty on-highway vehicles and work trucks but did not authorize NHTSA to set standards for engines on a standalone basis.”
EISA only required NHTSA to set fuel economy standards for vehicles, but not engines, federal officials explained.
NHTSA outlined the key components of the rule:
- Focus on Vehicles: The EISA explicitly directs NHTSA to establish a fuel efficiency program for commercial vehicles. Unlike the Clean Air Act – which gives the Environmental Protection Agency explicit authority to set emissions standards for engines – EISA contains no statutory authority for NHTSA to regulate engines or components like transmissions or tires.
- Alignment with Judicial Precedent: The interpretation applies the best reading of the law in light of the U.S. Supreme Court’s Loper Bright Enterprises v. Raimondo decision, as well as a recent decision from the U.S. Court of Appeals for the D.C. Circuit that found the agency has no authority to regulate the fuel efficiency of non-vehicle components.
- Support for Market Flexibility: Regulating complete vehicles gives manufacturers greater flexibility to innovate and tailor designs to the real-world operational demands of commercial customers that could include improvements to the engine as well as other parts of the vehicle such as transmissions, cab design, and tires.
“American innovators – not Big Government – know how best to design vehicle engines. The Trump Administration is getting out of the way so manufacturers can decide how they want to meet fuel efficiency requirements,” said NHTSA Administrator Jonathan Morrison. “Ensuring the commercial truck fuel efficiency program complies with Federal law will also lower commercial truck prices and allow American manufacturers – and the thousands of hardworking people they employ – to thrive.”
The NHTSA plans to update enforcement of the engine fuel efficiency standards outlined in the new rule pending the rulemaking process.