The 57.98 million-share, or roughly 10.8 percent, stake was revealed in a Friday night filing with the U.S. Securities and Exchange Commission. Phillips 66 shares closed Friday at $77.23. Berkshire once held a large stake in the Houston-based company, but shed nearly two-thirds of it in February 2014 when it swapped $1.35 billion of shares for a chemicals business that it folded into its Lubrizol unit.