Warren Buffett raised his stake in oil refiner Phillips 66 by 537,968 shares, according to a Securities Exchange Commission filing released Wednesday
The company's stock was slightly higher midmorning Thursday.
As of May 23, Berkshire Hathaway, Buffett's massive conglomerate, held a 14.88 percent stake, or more than 75 million shares, in Phillips 66 worth $6.17 billion, according to FactSet.
Phillips 66 shares are down about 1 percent year to date, but have fallen more than 10 percent over the past six months.
PSX 6-month chart