Reuters: President Barack Obama on Tuesday will announce the most aggressive proposal for increasing auto fuel economy standards ever and the first plan for regulating emissions, the White House said. The proposal would require the U.S. passenger vehicle fleet to average 35.5 miles per gallon (6.62 litres/100km) by 2016, saving 1.8 billion barrels of oil. It would also instruct the Environmental Protection Agency to regulate tailpipe emissions. Obama is expected to unveil the proposal …