Since agreeing to tough new federal fuel economy standards five years ago, automakers have been methodically improving the gas mileage of their vehicles and reducing emissions harmful to the environment, writes the New York Times. But despite investing billions in fuel-saving technologies and introducing a raft of lower-mileage models and electric cars, the industry will be hard-pressed to meet its target of 54.5 miles per gallon in 2025. Now, with a crucial midterm review of federal fuel-economy rules to begin this summer, automakers are expected to seek adjustments to the government’s formula for increasing mileage and cutting greenhouse gas emissions.