In morning trade, New York's main contract, West Texas Intermediate (WTI) light sweet crude for October delivery eased 10 cents to USD 85.20 a barrel and Brent North Sea crude for October delivery rose 19 cents to USD 110.81.
Bernanke is set to speak later in the day at a central bankers' conference in Jackson Hole, Wyoming, where his speech will be under heavy scrutiny for clues on whether he will push for further measures to bolster the sagging US economy.
The US is the world's biggest oil-consuming nation.
"We are waiting to see what the Fed has to say," said Bart Melek, head of commodity strategy for TD Securities.
The unrest in Libya, where pockets of resistance from forces loyal to strongman Muammar Gaddafi remained in parts of the capital Tripoli, was a factor in underpinning Brent crude prices.
Brent is more affected than WTI by the situation in Libya as oil from the North Sea as well as from Libya serve the European markets.
Around 85 per cent of Libyan oil output was exported to Europe until the revolt disrupted the country''s production six months ago.
Meanwhile, new weather forecasts that Hurricane Irene was no longer bearing down on the US Gulf of Mexico coast -- home to many refineries and offshore oil rigs -- and was instead heading for the US east coast brought relief to the markets.