The lawsuit alleges that NHTSA is violating a Congressional mandate to set fuel economy standards to the “greatest extent practicable.”
Published October 2, 2026
Twenty-six states, including California and New York, have filed a lawsuit against President Donald Trump’s administration after the U.S. Department of Transportation lowered fuel economy standards for gasoline-powered vehicles.
The lawsuit, filed Friday, challenges the Department of Transportation’s reduction in fuel efficiency standards to 34.9 miles (56 kilometers) per gallon (3.78 liters) per gallon by the 2031 model year. Under former President Joe Biden’s administration, fuel efficiency standards were set at 50.4 miles per gallon by the 2031 model year.
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California Attorney General Rob Bonta, who is leading the lawsuit, argued that the Trump administration improperly changed the way federal regulators calculate fuel economy standards.
The National Highway Traffic Safety Administration (NHTSA) sets standards based on technological improvements that increase the efficiency of gasoline-powered vehicles. To do this, we first model current vehicle performance and then consider what additional steps manufacturers can take to improve fuel efficiency over and above that in future model years.
Under previous standards, including during the first Trump administration, NHTSA’s base fleet included the millions of electric vehicles already on U.S. roads.
Mr Bonta said the Department for Transport’s changes ignored existing EV standards, making it easier to justify weaker standards for petrol vehicles, calling the approach “flawed” and “grossly distorted”.
The lawsuit also alleges that NHTSA’s new rules violate the law and that NHTSA violates its mandate from Congress to set fuel efficiency standards at the “highest practicable” level.
The Department of Transportation said the changes could save U.S. taxpayers $138 billion over the next five years.
“The president started a war, created instability in oil markets, disrupted the world’s energy supply, and made families and businesses pay the price. Yet the Trump administration is watering down fuel economy standards, forcing Americans to spend billions more on gasoline and polluting the air in our communities.”
This turnaround was praised by automakers.
“We welcome the administration’s efforts to reset CAFE (Corporate Average Fuel Economy) regulations to more achievable goals that align with market realities,” said Shane Kerr, senior vice president of public affairs for Stellantis North America.
Second lawsuit
The states’ lawsuit comes alongside a second lawsuit filed Friday by progressive and climate groups including the Environmental Defense Fund and Public Citizen.
“Trump’s lawless push to roll back key fuel economy safeguards will pollute our air and line the pockets of oil company and auto CEOs,” Robert Wiseman, co-director of Public Citizen, said in a statement announcing the lawsuit filed in federal court in Washington, D.C. “Trump’s lawless push to roll back key fuel economy safeguards will pollute our air and line the pockets of oil company and auto CEOs. We are confident in blocking Trump’s rollback of the CAFE standards.”
Auto stocks trended lower throughout the day, with Ford, General Motors and Toyota closing about 1% lower. Stellantis fell more than 6% after reports of poor sales.
