The Trump administration released revised Corporate Average Fuel Economy standards that set the requirement for 2031 model-year vehicles at 34.9 miles per gallon, compared with 50.4 miles per gallon under Biden administration rules. President Trump said the changes would support domestic automakers and lower consumer costs, while Transportation Secretary Sean Duffy called them a repeal of an illegal mandate favoring electric vehicles. Experts and California officials said the rules will allow larger, heavier and less efficient vehicles, raising fuel costs and complicating the state’s climate and clean-car goals. California is also facing the possible loss of federal authority over tailpipe emissions and its plan to end sales of new gasoline-powered cars in 2035. The administration said the standards would reduce oil consumption by about 1.3 billion barrels by 2050, while an earlier NHTSA estimate projected substantially larger gasoline and emissions savings under the Biden-era rules. California, other states and environmental groups are expected to challenge the changes in court.