Crude prices fell slightly Tuesday amid uncertainty surrounding US budget talks and caution ahead of the weekly release of US oil supply data.
New York's main contract, West Texas Intermediate for delivery in January, finished at $88.5 a barrel, down 59 cents from Monday's closing level.
In London trade, Brent North Sea crude for January fell $1.08 to $109.84.
On Wednesday, the US Department of Energy is due to issue its regular weekly report on US oil supplies, with analysts polled by Dow Jones Newswires predicting it would reflect a decrease of 400,000 barrels.
The closely watched data is considered a barometer of demand in the world's biggest crude-oil consuming country.
Crude oil prices dipped because investors appeared cautious ahead of Wednesday's inventory figures, said iiTrader's Bill Baruch.
Earlier Tuesday, the US Energy Information Administration reported that US monthly crude oil production reached its highest level in nearly 15 years, averaging almost 6.5 million barrels per day in September 2012. The last time the United States produced this much per day was in January 1998.
Markets also were closely watching a budget impasse in Washington that could send the world's biggest economy into recession if no deal is reached to avert the year-end "fiscal cliff" of significant tax increases and spending cuts that take effect in January.
Investors fear that if Republicans and Democrats fail to reach a compromise on longer-term budget-deficit reduction to avoid the cliff, demand for crude will drop.