The Trump administration says its proposal to roll back vehicle fuel economy standards, announced officially in the Oval Office on Wednesday, is an attempt to shave dollars off the ballooning cost of new cars in the US. It would also likely force Americans to pay more, long-term, at another place they tend to visit more frequently: the pump. The rollback is part of a larger federal about-face on not only auto policy, but the government’s attitude on climate change. Light-duty cars and trucks alone are responsible for some 15 percent of US greenhouse gas emissions, according to the US Environmental Protection Agency. The last Trump administration rolled back fuel economy standards, too.