Oil prices were mixed Thursday ahead of the release of data on U.S. crude stocks.

Investors are also watching for testimony by incoming Federal Reserve chief Janet Yellen for clues about when the U.S. will cut back, or taper, its $85 billion monthly bond purchases that have kept interest rates low to support economic recovery.

Benchmark U.S. crude for December delivery was down 4 cents to $93.84 a barrel at midafternoon Kuala Lumpur time in electronic trading on the New York Mercantile Exchange. The contract gained 84 cents to close at $93.88 on Wednesday.

Brent crude, the international benchmark, was up 39 cents to $107.29 a barrel on the ICE exchange in London.

The U.S. benchmark is down by about 8 percent in the past month. Traders say further declines are likely.

U.S. crude stockpiles data for the week ended Nov. 8, due later Thursday, are expected to show an increase of 1.8 million barrels, according to a survey of analysts by Platts, the energy information arm of McGraw-Hill Cos. It would the eighth week in a row that stockpiles have risen, suggesting weak demand.

Yellen, who is set to replace Ben Bernanke as Fed chairman at the end of January, will testify before the Senate banking committee later Thursday.

In published introductory remarks, she indicated that Fed's stimulus should continue until the world's No.1 economy show continued signs of improvement.

In other energy futures trading on Nymex:

— Wholesale gasoline added 2.7 cents to $2.64 a gallon.

— Heating oil shed 0.2 cent to $2.90 a gallon.

— Natural gas fell 2.7 cents to $3.539 per 1,000 cubic feet.