New York: Oil prices rallied for a fifth straight session on Wednesday as official data showed US crude stockpiles dropped last week. US oil inventories fell 2.5 million barrels last week, surprising analysts who had expected a build of 522,000 barrels, the Energy Information Administration (EIA) said in its weekly report on Wednesday, Xinhua news agency reported. US gasoline stockpiles also fell 2.7 million barrels, more than expectations of a 1.6 million-barrel drop, the EIA report showed. US oil has rallied more than 12 per cent over the past five sessions as speculation raised that the talks of Organization of the Petroleum Exporting Countries next month could result in a crude output freeze. The West Texas Intermediate for September delivery increased $0.21 to settle at $46.79 a barrel on the New York Mercantile Exchange, while Brent crude for October delivery gained $0.62 to close at $49.85 a barrel on the London ICE Futures Exchange.