Occidental Petroleum is getting a boost from Warren Buffett once again as the legendary investor bumped his stake in the oil giant to more than 20%. Shares of Occidental jumped more than 4% on Tuesday after a regulatory filing Monday night showed that Buffett’s Berkshire Hathaway holding company paid about $391 million for nearly 6.7 million additional shares of the energy name between last Thursday and Monday. After steadily ramping up its stake, Berkshire now owns 188.5 million shares of Occidental, equal to a 20.2% position. It surpassed a key threshold where Berkshire could record some of the oil company’s earnings with its own, potentially adding billions of dollars in profit. GAAP (generally accepted accounting principles) recommends investors include a proportionate share of a company’s earnings in their own results once they own at least 20% of the company’s common stock. Berkshire, Occidental’s biggest single shareholder by far, could increase its reported profit by roughly $2 billion, which is 20% of Occidental’s expected earnings, according to FactSet’s survey of analysts. Berkshire’s operating earnings — encompassing profits made from an array of businesses including insurance, railroads and utilities — totaled $9.283 billion in the second quarter . That marked a 38.8% increase from the same quarter a year ago. Occidental has been the best-performing stock in the S & P 500 this year, up about 113% so far, on the back of surging oil prices. Buffett’s bet on Occidental has inspired a legion of small investors to follow suit, making it a favorite retail stock this year, according to data from VandaTrack. Berkshire also owns $10 billion of Occidental preferred stock, and has warrants to buy another 83.9 million common shares for $5 billion, or $59.62 each. The warrants were obtained as part of the company’s 2019 deal that helped finance Occidental’s purchase of Anadarko . The stake would rise to nearly 27% if Berkshire exercises those warrants. The move also sparked speculation as to whether Berkshire will eventually acquire the whole company. “Buffett has said previously that he would be happy to own 100% of the companies that he buys … for the right price,: said Bill Stone, CIO of The Glenview Trust Company. “I’d say that OXY fits some of his recent purchases that need capital investment but can throw off significant cash flows. OXY has lots of debt, but Berkshire has cash.” Cathy Seifert, a Berkshire analyst at CFRA Research, said she believes Occidental will remain a strategic equity investment for Berkshire.