The market's muted reaction to a sharper-than-expected drawdown in US crude stocks also reflected growing concerns that high prices may eventually take their toll on consumers, they said.
In early morning trade, New York's main contract, light sweet crude for January delivery fell 79 cents to 86.70 US dollars a barrel from 87.
49 dollars in late US trades Wednesday.
Brent North Sea crude for January delivery dropped 49 cents to 88 dollars a barrel.
"The subdued price reaction may be due to the markets pondering why OPEC rolled over ... concerns about economic and oil demand growth," said French banking giant Societe Generale.
The Organisation of the Petroleum Exporting Countries (OPEC) decided at a meeting on Wednesday to maintain its daily production quota at 27.
25 million barrels.
The United States, the world's biggest energy user, has earlier called on the cartel to pump more crude to cool oil prices which surged to record high levels of above 99 dollars last month.