Oil prices slid on Wednesday, falling under 79 dollars as traders eagerly awaited this week's update on energy stockpiles in key consumer the United States.

New York's main contract, light sweet crude for December delivery, lost 62 cents to 78.93 dollars a barrel.

Brent North Sea crude for December shed 61 cents to 77.31 dollars.

Later Wednesday, the US government's Department of Energy (DoE) will release its weekly snapshot of American crude stockpiles for the week ending October 23.

Market expectations are that US gasoline (petrol) reserves fell 1.2 million barrels last week, according to analysts polled by Dow Jones Newswires.

Stockpiles of distillates, which include diesel and heating oil, are seen declining by 1.1 million barrels. Crude reserves are expected to climb by 1.4 million barrels.

"Today, we are closely monitoring US distillate stockpiles with the release of the weekly US fuel inventories," said VTB Capital analyst Andrey Kryuchenkov.

"Colder weather in the US will in our view support demand for distillates, while we expect crude stocks to rise on the back of relatively strong imports," he said.

Investors were also cautious ahead of Thursday's official gross domestic product (GDP) figure for the US economy.

Most analysts say GDP will see a 3.2 percent expansion, the first growth for the world's largest economy after a year of contractions.

Crude prices hit 82 dollars last week, the highest since October 2008, partly on the back of a weak US currency which makes dollar-priced crude cheaper for holders of stronger foreign units.