SINGAPORE (Reuters) – Asian oil traders are stumped by how Saudi Arabia derived its official selling prices (OSP) for May after the world’s top oil exporter unexpectedly raised the price for its flagship Arab Light crude sold to Asian refiners. FILE PHOTO: A view shows Saudi Aramco’s Abqaiq oil facility in eastern Saudi Arabia in this undated handout photo. Saudi Aramco/Handout/File Photo via REUTERS State oil giant Saudi Aramco deviated from its usual pricing formula by increasing Arab Light’s official selling price for May by 10 cents per barrel to a premium of $1.20 a barrel to the average of Oman and Dubai quotes. Market participants were expecting a cut of between 50 cents to 60 cents a barrel in a Reuters survey published earlier this week. “This is a very unusual OSP,” a trader with a North Asian firm said. “It’s not in line with the past method […]