Oil prices drifted lower in thin trade ahead of this afternoon's US inventory data in which the market has already priced in a large crude stock fall. At 10.29 am, September-dated Brent futures contracts were down 27 cents at 57.73 usd a barrel. Meanwhile, US benchmark September-dated contracts were down 28 cents at 58.97, in pre-market deals. "The market is expecting large crude stock fall this afternoon, which it has already factored in," said Informa Global Markets analyst Peter Luxton. Luxton said he expects to see a fall in crude stockpiles of at least 2.3 mln barrels for the week ending July 15. An early start to the US hurricane season in which a series of storms have caused disruption to oil and gas production. Last week's crude stock draw-down was a modest 900,000 barrels, and analysts are expecting the losses to be reflected in this afternoon's figures. In addition Luxton said he is expecting to see a rise in distillate stocks of around 1.7 mln barrels. Distillates stocks have risen for ten successive weeks. Refineries have been pushing to maintain high production levels to dampen jitters of a supply squeeze in the fourth quarter. "Distillates is the one to watch, if there is an above expected rise then (oil) prices could turn lower," he said. Separately, US oil refining giant Valero yesterday announced it has planned overhauls for later in the year. The work includes 18 days of work in September at three of its facilities.