Ample global supply and increasing U.S. commercial inventories weighed on U.S. crude prices on Thursday after expectations for better demand going forward lifted prices a day earlier, traders and analysts said.
U.S. crude settled 5.5 percent lower, or $2.82, at $48.17 a barrel, following a more than 3 percent gain in the previous session.
Brent losses were tempered by expectations for improving global demand and geopolitical concerns about energy supplies from Libya and Russia.
Benchmark Brent crude fell $1.60 to $60 a barrel, after hitting a session peak of $62.63. On Wednesday, Brent surged 5 percent.
Earlier, Brent's premium to U.S. crude increased to $12.06 intraday on Thursday, the widest since January 2014.