Oil prices ended mixed in volatile trade on Wednesday, with global benchmark Brent up on worries about Russian airstrikes in Syria and U.S. crude down after data showing a surge in domestic inventories.
For the quarter, both Brent and U.S. crude were down 24% for their sharpest decline since the end of 2014.
Oil prices were broadly boosted in early trade by concern about a hurricane threatening energy infrastructure on the U.S. East Coast. Book balancing by traders at the end of the month and the third quarter also made for choppy trade.
"It's the typical month-end, quarter-end 'window dressing' phenomenon," said Tariq Zahir, fund manager and crude oil spreads trader at Tyche Capital Advisors in Laurel Hollow, New York.
Warplanes from Russia carried out air strikes against Islamic State targets in Syria, feeding worries about growing war in the Middle East.
The U.S. National Hurricane Center said it expected Hurricane Joaquin to reach the Bahamas on Wednesday night. The storm might move north to threaten the New York Harbor, delivery point for the U.S. gasoline and ultra low sulfur diesel futures contracts.
"High seas along the East Coast have been forecast and that could affect barges carrying refined products," said David Thompson, executive vice-president at Washington-based commodities broker Powerhouse.
Brent settled up 14 cents, or 0.3%, at $48.37 a barrel. It fell 10% for September .
U.S. crude settled down 14 cents, or 0.3%, at $45.09, surrendering earlier gains. For the month, U.S. crude was down 8%.
Crude inventories in the United States rose by nearly 4 million barrels last week, government data showed, versus a 1 milllion-barrel rise forecast by analysts in a Reuters poll.
Gasoline stockpiles rose more than 3 million barrels, compared with the poll's forecast for a 40,000-barrel draw, the data from the Energy Information Administration (EIA) showed.
But the EIA also announced drawdown of 1 million barrels at the Cushing, Oklahoma, delivery hub for the U.S. crude oil futures contract. U.S. crude got a brief boost from the Cushing storage data, which is key to the market's psyche.
Separately, the EIA said U.S. oil output in 2016 was expected to be at just under 9 million barrels per day. It was the second time in two months that the EIA slashed its production forecast by 400,000 bpd.
(By Barani Krishnan; Additional reporting by Karolin Schaps in London, Aaron Sheldrick in Tokyo and Henning Gloystein in Singapore; editing by David Gregorio and Cynthia Osterman)