California has issued subpoenas to Valero Energy Corp and Chevron Corp as part of a probe into whether oil refiners in the state have manipulated gasoline prices since 2014, the companies said on Thursday. Shell, Tesoro Corp, Phillips 66, and Exxon Mobil and other major refiners are also under investigation, the Wall Street Journal first reported on Thursday, citing people familiar with the matter. California Attorney General Kamala Harris sent subpoenas to the companies in May requesting information on trading, maintenance and repair activities to determine if refiners in the state withheld supply to lift gasoline prices, the Journal said. “We can’t confirm or deny any subpoenas,” Kristin Ford, deputy communications director for Harris’ office, said by email. Harris, a Democrat, is running for the U.S. Senate in November. California has the most expensive gas in the continental United States, in part due to special blending specifications mandated by […]