Berkshire filed documents with the Securities and Exchange Commission on Friday that disclosed purchases of another 1.6 million Phillips 66 shares.
Buffett's company has now bought nearly 7.5 million shares of Phillips 66 this month. It's possible the buying may continue because Phillips 66 share prices haven't increased above the range where Berkshire has been buying.
Berkshire first revealed owning over 10 percent of Phillips 66 stock in August when it disclosed a stake of 55 million shares. This month's purchases are the first Berkshire made since September.