The Trump administration finalized a major rollback of federal fuel-economy requirements Monday, lowering the target for the nation’s vehicle fleet in 2031 from 50.4 miles per gallon to 34.9 mpg. The change replaces standards adopted under President Joe Biden that would have increased fuel-economy requirements by 2% annually for model years 2027 through 2031. The Trump administration says its revised standards will make new vehicles an average of $1,300 cheaper. The potential trade-off is higher fuel use. The Biden administration estimated its standards would save drivers more than $600 in gasoline costs over a vehicle’s lifetime. Opponents of the rollback say less-efficient vehicles could mean greater fuel expenses for owners, more pollution and worsening climate change. President Donald Trump promoted the change in a Truth Social post over the weekend, describing the previous rules as an electric-vehicle mandate. The requirements set fuel-economy targets for automakers; the supplied policy details do not describe them as requiring consumers to buy electric vehicles. The standards had already been weakened when a provision in Trump’s “Big Beautiful Bill” reduced penalties for failing to meet them to zero. With the new rule finalized, automakers are no longer legally required to comply with the standards, according to the reported policy details. For drivers, the competing cost claims point to two different parts of vehicle ownership: the price paid when buying a car and the fuel costs that accumulate over years of use. The rollback also changes federal policy intended to improve fleet efficiency, with potential consequences for fuel consumption and emissions.