China’s crude oil output dropped to the lowest in more than six years as the country’s state-run energy giants continued to pump less from aging, high-cost fields. Production during August in the world’s largest energy consumer dropped 9.9 percent from a year ago to 16.45 million tons, according to data from the National Bureau of Statistics on Tuesday. That’s about 3.89 million barrels a day, the lowest since December 2009, according to Bloomberg calculations. Output is down 5.7 percent during the first eight months of the year.