The Trump administration on Monday finalized a change to federal fuel-economy rules that will require automakers to make their new-car and truck fleets more efficient at a slower pace, reversing stricter targets adopted under President Joe Biden. Under the new Corporate Average Fuel Economy (CAFE) standards, automakers must increase fuel efficiency by as much as 1% annually, with a fleet average of 34.9 miles per gallon for model year 2031. The Biden-era rules called for annual gains of 2% and an average of 50.4 mpg by 2031. The Transportation Department says easing the requirements will reduce the cost of building vehicles and lower new-car sticker prices by about $1,300. Transportation Secretary Sean Duffy said the administration was providing relief to families and supporting U.S. manufacturing. President Donald Trump also argued the revised standards would mean lower prices for buyers. But the price effect is disputed. Sue Helper, an auto-industry economist at Case Western Reserve University, said vehicle prices have risen for reasons including the shift toward larger SUVs, tariffs, supply-chain disruptions and added features. A 2023 Consumer Reports analysis found that vehicles became about 30% more fuel-efficient between model years 2003 and 2021, while attributing much of the price increase to automakers’ move toward more expensive SUVs. Less efficient vehicles can also cost more to operate because drivers buy more gasoline. The national average was close to $4.50 a gallon on the day the rule was announced, according to AAA. Dan Becker of the Center for Biological Diversity said the rollback could raise fuel use and pollution, adding costs both at the pump and through health effects. The final rule also ends a system that let automakers buy fuel-economy credits from companies producing electric vehicles to help meet their targets. The Biden-era standards had made electric vehicles one way for manufacturers to offset less-efficient models; penalties for missing the standards had already been eliminated under legislation enacted in July. Automakers and their industry trade group welcomed the new rule, saying the prior targets were out of step with customer demand and market conditions. But Helper and other critics cautioned that giving manufacturers less pressure to improve efficiency could slow innovation and weaken their ability to compete in markets where fuel and emissions rules are stricter. Ellen Hughes-Cromwick, a former Ford chief global economist, said the broader industry is moving toward electric vehicles and that U.S. companies face competition from China. CAFE standards date to a 1975 law enacted after an oil-supply shock, when Congress sought to reduce U.S. dependence on imported oil. The latest rollback follows other Trump administration actions affecting climate and vehicle policy, including ending a federal tax credit for electric-vehicle buyers and challenging California’s authority to impose stricter vehicle-pollution rules. The final rule could face legal challenges, and a future administration could set more demanding standards again. That uncertainty matters to automakers, which make long-term decisions about vehicle models and factory investments well before cars reach showrooms.