Oil refiners’ investment in more-efficient refinery facilities is leaving shipping lines competing with Japanese power producers for a fuel no one wants to make. Refiners are upgrading plants to cut output of fuel oil, a byproduct of making gasoline and diesel, as it sells for less than the price of crude. Shipping lines are seeking more of the product -- known in the industry as bunker -- to fuel expanding fleets, while Japanese electric companies are speeding purchases as they close nuclear plants for safety checks following 2011’s tsunami. “We have a bunker market which is still growing, and we have no fuel,” said Fereidun Fesharaki, chairman of Singapore-based Facts Global Energy Inc.