The Transportation Department on Sept. 28 released final fuel economy standards that sharply lower requirements for new cars and light trucks, and environmental and public health groups immediately pledged to challenge the rule. The National Highway Traffic Safety Administration projects the standards will produce a fleetwide average of 34.9 miles per gallon by model year 2031, up from 30.1 mpg in model year 2024, according to the Transportation Department's announcement.

That 2031 figure is far below the 50.4 mpg projected under the standards adopted in 2024. The new rule also ends trading of fuel economy compliance credits between automakers for credits earned beginning in model year 2028.

The change matters for households because fuel economy rules shape what kinds of vehicles automakers build and how much fuel those vehicles burn over a decade or more on the road. Supporters say the rule will make cars more affordable. Critics say it will cost drivers more at the pump and add to air and climate pollution.

The Rule at a Glance

Corporate Average Fuel Economy, or CAFE, standards grew out of a 1975 law passed after the oil embargo of the early 1970s. They set average mileage targets across each automaker's fleet rather than for individual models. The program remains in place. What changed is how quickly the targets rise.

NHTSA Administrator Jonathan Morrison signed the final rule on Sept. 25, and the agency has submitted it for publication in the Federal Register, according to the final rule document posted by NHTSA. The rule takes effect 60 days after publication. The proposal, called the SAFE Vehicles Rule III, appeared in the Federal Register in December 2025.

The department said the standards will reduce yearly oil consumption in 2050 by about 1.3 billion barrels compared with 2024. It also said the rule will cut the average cost of a new vehicle by $1,300 and save Americans $138 billion over five years. Beginning with model year 2030, the rule changes how vehicles are classified as passenger cars or light trucks, which the department expects to flip the current fleet mix of roughly 70 percent light trucks to roughly 70 percent passenger cars.

The 34.9 mpg figure is a fleetwide compliance projection, not the number a driver will see on a window sticker. NHTSA notes in the rule that real-world fuel economy is generally 20 to 30 percent lower than the compliance figure.

Automakers Praise the Change

Industry groups and automakers welcomed the rule. John Bozzella, president and CEO of the Alliance for Automotive Innovation, said NHTSA "made the right call," adding: "Today's final rule is an appropriate course correction."

A General Motors spokesperson said the company supports the rule's intention "to better align fuel economy standards with market realities," PBS NewsHour reported. Ford said it would keep working with the administration as it evaluates the rule's full impact on its business, and Stellantis also welcomed the changes.

The department argues that the 2024 standards went beyond what Congress required and pushed manufacturers toward electric vehicles. NHTSA did not consider the fuel economy of electric vehicles or the electric operation of plug-in hybrids in setting the new standards, an approach it says the law requires.

Environmental and Health Groups Push Back

Environmental groups criticized the rule as a step backward for drivers and air quality. "Less fuel-efficient cars mean more gas burned, spending more at the pump," said Katherine García, director of the Sierra Club's Clean Transportation for All campaign, who said the group would fight the rule.

Dan Becker, director of the Center for Biological Diversity's Safe Climate Transport Campaign, said the rule "ignores the feasibility of clean technology."

Health advocates raised concerns as well. Harold Wimmer, president and CEO of the American Lung Association, said the rule "will create more air pollution, harm health and accelerate climate change," according to Inside Climate News. Jason Schwartz of New York University's Institute for Policy Integrity told the outlet that the 2024 standards had been projected to save consumers about $80 billion in fuel costs.

The basic physics behind the critics' argument is not in dispute. Burning more gasoline releases more carbon dioxide, and transportation accounts for about 28 percent of U.S. greenhouse gas emissions, according to EPA emissions data. The debate is over how much additional fuel the rule will cause drivers to burn, how vehicle prices will change, and whether the department's cost-benefit analysis holds up.

Costs, Lawsuits and Unanswered Questions

For a typical household, the effects will arrive slowly. The rule applies to new vehicles, so drivers keeping their current cars see no direct change. Buyers of future model years may find lower sticker prices if automakers pass on savings, but they could also pay more for fuel over the life of a less efficient vehicle. Which effect is larger will depend on gas prices, driving habits and how automakers respond.

The rule arrives as gasoline averaged $4.47 a gallon on Sept. 28, up from $3.13 a year earlier, according to AAA figures cited by the Associated Press.

The rule also follows earlier changes. Legislation enacted in July 2025 set civil penalties for missing CAFE targets at zero, and the administration has rolled back federal tailpipe emissions rules and ended consumer tax credits of up to $7,500 for electric vehicles. Together, those moves reduce the pressure on automakers to sell more efficient vehicles.

Several questions remain open. Environmental groups have pledged to challenge the rule, but no lawsuit had been reported as of its release, and it is unclear which court would hear one. Readers shopping for a car can still compare real-world fuel costs using the EPA ratings on window stickers, which remain the best guide to an individual vehicle's efficiency.

What Readers Want to Know

What did the new fuel economy rule change?

NHTSA lowered its fuel economy standards for cars and light trucks, projecting a fleetwide average of 34.9 mpg by model year 2031 instead of the 50.4 mpg projected under the 2024 rule.

Does this end federal fuel economy standards?

No. The CAFE program remains in place. The rule slows how quickly mileage targets rise and ends credit trading for credits earned starting in model year 2028.

Will my car get worse gas mileage?

No. The rule affects future new vehicles, not cars already on the road. The 34.9 mpg figure is a fleet compliance average, not a sticker rating.

Who supports the rule?

The Transportation Department, the Alliance for Automotive Innovation, GM, Ford and Stellantis have welcomed the change, saying it aligns standards with the law and market conditions.

Who opposes it?

The Sierra Club, the Center for Biological Diversity and the American Lung Association criticized the rule over fuel costs, air pollution and climate effects, and groups say they will challenge it.

When does the rule take effect?

NHTSA signed the rule on Sept. 25 and submitted it to the Federal Register. It takes effect 60 days after publication.