President Donald Trump said Saturday, Sept. 26, that he had approved new fuel economy standards that would roll back Biden-era requirements. The final rule had not been published as of Sunday, Sept. 27; Reuters reported that the Transportation Department planned to finalize the standards Monday, Sept. 28.
The administration’s proposal would lower the projected fleetwide average for model year 2031 from 50.4 miles per gallon under Biden-era standards to 34.5 mpg. That is an average across manufacturers’ fleets, not a mileage requirement for every car or truck.
The department’s estimates describe a trade-off: average new-vehicle costs could fall, while fuel use, fuel spending and carbon dioxide emissions could rise. Those are projections, not results already measured on roads or in household budgets.
What would Trump’s proposed fuel economy standards change?
The Corporate Average Fuel Economy program, known as CAFE, sets fuel-economy standards for manufacturers’ fleets of passenger cars and light trucks. The National Highway Traffic Safety Administration’s overview explains that compliance is assessed across fleets, rather than by requiring every individual vehicle to achieve the same mileage.
The Trump administration’s December 2025 proposal would reset CAFE standards for model years 2022 through 2031. The Transportation Department’s proposal lays out three central changes:
- A lower projected average. The proposal estimates a fleetwide average of 34.5 mpg for model year 2031. Reuters reported that the Biden-era standards projected 50.4 mpg for that year.
- A slower pace of annual increases. The proposal calls for increases ranging from 0.25% to 0.5% a year, depending on vehicle category and model year. Biden-era rules required increases of 8% in model years 2024 and 2025, 10% in 2026, and 2% annually from 2027 through 2031, Reuters reported.
- Different compliance calculations. The proposal would leave electric vehicles out of CAFE calculations and end trading of credits between manufacturers beginning in model year 2028.
Because CAFE uses fleet averages, the proposed 34.5-mpg figure does not mean every vehicle a company sells must reach that mileage. The mix of passenger cars and light trucks a manufacturer sells matters to its average, as do the rules for which vehicles and compliance options count. Excluding EVs from the calculation would change that accounting; it does not establish what automakers will build or what buyers will choose.
The proposed annual increases vary by vehicle category and model year, and are far below the increases specified for several recent model years under the Biden-era rules. The precise requirements and calculations could change in the final rule. As of Sunday, its text and effective dates were not available.
What could drivers pay at the dealership and the pump?
The Transportation Department estimates that its proposal would reduce average new-vehicle costs by $930 per vehicle. That is an agency projection, not a guaranteed price cut for every buyer or model.
The same estimates point to costs after purchase. Reuters reported that the department projected about 100 billion gallons of additional fuel consumption and $185 billion in fuel spending through 2050. It also projected an approximately 5% increase in carbon dioxide emissions over that period.
The $185 billion figure is a projected increase over time, not an annual bill or a cost assigned to each driver. Likewise, the $930 estimate is an average for new vehicles, not a promise about any particular model’s sticker price. The figures are forecasts, not verified changes in what people have paid or how much fuel vehicles have used.
That distinction matters to the administration’s affordability argument. Lower projected purchase costs could help people shopping for a vehicle, while higher projected fuel use and spending could affect owners over time. The estimates do not show how those costs would be distributed among drivers or how actual prices and fuel use would change if the proposal takes effect.
A lower CAFE target could change automakers’ incentives to improve fleet fuel economy, but the proposal alone cannot show how companies will respond. The final calculation methods and the vehicles manufacturers choose to sell will shape the result; neither is fully known from the proposal. The figures also do not establish what an individual driver would save or spend over the life of a vehicle.
How do the proposed targets compare with Biden-era standards?
The Biden-era standards followed an earlier round of changes. In April 2022, NHTSA announced requirements intended to bring the industry fleet average to about 49 mpg for model year 2026, according to the agency’s announcement. In June 2024, the agency finalized standards for passenger cars and light trucks through model year 2031. Its final-rule document estimated an average of about 50.4 mpg by 2031.
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Trump and Transportation Secretary Sean Duffy have presented the rollback as a way to reduce vehicle prices and end what the administration portrays as a Biden-era EV mandate. But the Associated Press reported that Biden-era policies did not require automakers to sell EVs or consumers to buy them.
Duffy presented the proposed change as a win for auto workers, Reuters reported. Pete Buttigieg, who served as transportation secretary under Biden, criticized the proposal, arguing that it could weaken the United States’ position in clean technology and increase drivers’ costs at the pump.
Katherine García, director of the Sierra Club’s Clean Transportation for All campaign, opposed the proposal, saying it could prolong the use of polluting vehicles and threaten public health, the Associated Press reported. The department’s projected increase in fuel use and carbon dioxide emissions does not establish what the proposal’s eventual effects on public health would be.
The rule concerns fuel-economy standards for manufacturer fleets. Its modeled emissions increase is a forecast tied to the proposal, not a measured outcome. The exact effect on real-world vehicle emissions will depend on the final rule and what happens after it takes effect.
What remains unknown before the rule is finalized?
Until a final text is published, it is unclear whether the department will retain the proposed 34.5-mpg projection, exclude EVs from CAFE calculations and end credit trading as planned. The exact compliance provisions and effective dates also remain unsettled.
The proposal changes the standards manufacturers would have to meet as fleets; it does not determine which models they will make or how much those vehicles will cost. The reporting available Sunday did not establish how automakers or their trade groups viewed Trump’s announcement.
Reuters reported that the department expected to finalize the standards Monday, Sept. 28. Until then, drivers and automakers have a proposal and agency projections, not a final account of how the standards will apply or what effects they will produce.