It was looking so good for oil... US prices for the commodity climbed to a six-week high on Tuesday, but dropped back from their back on Wednesday.

Prices were last down 0.6% at $56.88 a barrel, compared to Tuesday's peak of $57.50 per barrel.

The drop came on the heels of data from the American Petroleum Institute, which showed an unexpected increase in US inventories . Larger inventories of oil mean higher supply and therefore weigh on prices.

"The API number is less widely followed that the EIA but does give a possible heads up for what to possibly expect," said Craig Erlam, senior market analyst at Oanda.

The Energy Information Agency's inventory report for the week ended November 1 is due at 10 am ET.