President Donald Trump said on his Truth Social media account Saturday that the less stringent mileage requirements would “take the waste out of building cars in America” and save families “thousands on a new, beautiful and safe car,” while boosting auto production in the U.S.

Last December, the National Highway Traffic Safety Administration projected that the new standards would set the industry fleetwide average for light-duty vehicles at roughly 34.5 miles per gallon in the 2031 model year, down from a projected 50.4 miles per gallon in 2031 under rules put in place by the Biden administration.

Fuel economy requirements set out how far new vehicles need to travel on a gallon of gasoline. The change would further Trump’s promise to revoke policies that encouraged or created incentives for the production of electric vehicles.

Since taking office, Trump has relaxed auto tailpipe emissions rules, repealed fines for automakers that do not meet federal mileage standards and terminated consumer credits of up to $7,500 for EV purchases.

Secretary of Transportation Sean Duffy said Saturday on his social media account on X that the changes would be announced Monday. The White House, Department of Transportation and NHTSA couldn’t immediately be reached for comment on the details of the new standards.

General Motors, Stellantis, and Ford Motor, maker of the top-selling pickup truck, the F-150, also couldn’t be immediately reached for comment. The administration and automakers have said the new rules will increase Americans’ access to the full range of gasoline vehicles they need and can afford.

The average new car in America sold for $50,089 in August, crossing over the $50,000 line for the first time since last December, according to Kelley Blue Book data. At the same time, Americans are spending more on gas as Washington’s war with Iran disrupts the global flow of fuel. The national average price for a gallon of gas was $4.47 on Sunday, up from $4.09 a month ago, according to the AAA motor club.

Trump has repeatedly pledged to end what he falsely calls an EV “mandate,” referring incorrectly to President Joe Biden’s target that half of all new vehicle sales be electric by 2030. No federal policy has mandated auto companies to sell EVs.

According to data from the automotive research group Edmunds, EVs accounted for 6.5% of new vehicle sales in February, down from 7.4% for all of 2025.

News of the revised standards immediately drew rebukes from environmentalists.

Dan Becker, director of the Center for Biological Diversity’s Safe Climate Transport Campaign, said that the final rule “ignores the feasibility of clean technology and the millions of fuel-efficient cars already on the road.”

“Trump is tanking sensible mile per gallon standards at the worst possible time for consumers, who are getting hit with sky-high prices at the pump,” Becker said in a statement. “Consumers will pay the price for these reckless rollbacks while Trump’s Big Oil and Big Auto buddies reap the short-term profits.”

Katherine García, director of the Sierra Club’s Clean Transportation for All campaign, vowed the environmental group would fight the rule and said that the loosening of fuel standards would “make driving more expensive too.”

“Less fuel-efficient cars mean more gas burned, spending more at the pump, and dirtier air in our communities,” Garcia wrote in a statement.

When the 2024 standards went into effect, NHTSA estimated they would save 14 billion gallons of gasoline from being burned by 2050. The agency also said that while new fuel-efficient vehicles cost more up front, savings on gasoline over the lifetime of the car or truck would more than make up for that.

Without these standards, in 2035, cars could produce 22,111 more tons of carbon dioxide per year than under the Biden-era rules. It also translates to an extra 90 tons a year of deadly soot particles and 4,870 additional tons a year of smog components such as nitrogen oxides and volatile organic compounds emitted into the air in coming years.

Mileage standards, known as the corporate average fuel economy, or CAFE, have been implemented since the 1970s energy crisis, and over time, automakers have gradually improved their vehicles’ average efficiency.