Lawsuit alleges NHTSA contravenes its congressional mandate to set fuel-economy standards at ‘maximum feasible’ .
Published On 2 Oct 2026
Twenty-six states, including California and New York, have filed a lawsuit against United States President Donald Trump’s administration after the US Department of Transportation lowered fuel economy standards for petrol-powered vehicles.
The lawsuit, filed on Friday, challenges the Department of Transportation’s rollback of fuel economy standards to a fleet average fuel economy of 34.9 miles (56km) per gallon (3.78 litres) by model year 2031. Under the administration of former President Joe Biden, fuel economy standards were set at 50.4 miles (81km) per gallon by model year 2031.
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California Attorney General Rob Bonta, who is leading the lawsuit, argued that the Trump administration improperly changed how federal regulators calculate fuel economy standards.
The National Highway Traffic Safety Administration (NHTSA) bases standards on technological improvements that could make petrol-powered vehicles more efficient. To do that, it first models the current fleet’s performance and then considers what additional actions manufacturers could take to improve their fuel economy in future model years above that.
In past standards, including during the first Trump administration, NHTSA’s baseline fleet included the millions of electric vehicles that already run on US roads.
Bonta said the Transportation Department change ignores the existing slate of EVs, which makes it easier to justify weaker standards for petrol-powered vehicles, and called the approach “flawed” and “dramatically distorted”.
The lawsuit also alleges that NHTSA’s new rule is contrary to law and that NHTSA contravenes its mandate from Congress to set fuel-economy standards at their “maximum feasible” level.
The Transportation Department has said the change could save American taxpayers $138bn over the next five years.
“The president started a war that has created volatility in oil markets, disrupted global energy supplies, and left families and businesses paying the price at the pump. Yet, the Trump administration is attempting to gut fuel economy standards and force Americans to spend billions more on gas while poisoning the air in our communities,” Attorney General Bonta said in a statement.
The rollback was applauded by car makers.
“We welcome the Administration’s efforts to reset the CAFE [Corporate Average Fuel Economy] regulations to more achievable targets that are better aligned with market realities,” said Shane Karr, senior vice president of public affairs at Stellantis North America.
Second lawsuit
The litigation by the states came in tandem with a second lawsuit filed on Friday by progressive and climate groups, including the Environmental Defense Fund and Public Citizen.
“Trump’s lawless push to roll back key safeguards on fuel economy will pollute our air, and line the pockets of oil and auto CEOs. We are confident of stopping Trump’s CAFE standards rollback,” Robert Weissman, co-president of Public Citizen said in a statement announcing the lawsuit, which was filed in a federal court in Washington DC.
Auto stocks were trending downward throughout the day, with Ford, General Motors and Toyota closing down around 1 percent. Stellantis fell more than 6 percent amid reports of slumping sales.