They said growing concerns over the economic outlook in the United States, the world's largest energy consumer, had put pressure on the market.
New York's main contract, light sweet crude for delivery in February, gained 87 cents to 91.00 dollars per barrel.
Brent North Sea crude for March firmed 95 cents to 89.70 dollars.
"A lot (of oil's movement) will depend on the financial markets and other commodity markets," said Base Commodities trader Tony Machacek in London.
Equity markets have tumbled this week on fears of a US recession, a development that would dampen demand for energy in the world's biggest economy.
"The drop in demand is certain in the short term with the economic slowdown in the United States affecting sentiment worldwide," said Tony Nunan, of Mitsubishi Corp.'s international petroleum business in Tokyo.
"Everyone stops spending and that will drive prices further down," he said.
Trading was volatile and in a "worst-case scenario" prices could fall as low as 69 dollars, he added.
"I can see prices dropping to the lower 80s or even the higher 70s as we move towards the end of the first quarter."
US President George W. Bush was Friday to propose a series of "short-term, temporary measures" to stimulate the US economy to help it get past current troubles, the White House said.
"If the US falls into recession and China slows down, we could be headed for one of the most significant corrections of this decade in oil," said Phil Flynn, an analyst at Alaron Trading.
Prices remain at high levels but have shed more than 10 dollars since striking a record in New York of 100.09 dollars in early January.
They had tumbled Wednesday in reaction to a report of an increase in US crude reserves and after Bush called on OPEC members to hike output.
A day earlier, Bush voiced concern about high prices as he met King Abudullah of Saudi Arabia -- the world's biggest oil producer -- during a tour of the Middle East.
Traders are looking ahead to the February 1 meeting of the Organisation of the Petroleum Exporting Countries in Vienna.
On Wednesday, the International Energy Agency kept its 2008 forecast for oil demand unchanged despite growing expectations of a US recession.