Reuters: Mexico will limit imports of inefficient used cars and encourage low-carbon technology to reduce its overall volume of tailpipe exhaust, the energy ministry said on Tuesday. The ministry said it was also mulling regulations that would for the first time set a national standard for auto emissions. Such standards would be at the “vanguard” of international best standards, the agency said. Officials hope to slowly purge heavy, inefficient autos from among the roughly 21 million …