Oil prices were mixed on Friday at the end of a volatile week's trading that was dominated by a weak outlook for energy demand amid slowing economic growth.
New York's main contract, light sweet crude for delivery in October, fell 23 cents to $89.17 a barrel.
Brent North Sea crude for October gained 59 cents to $112.89 in midday London deals.
"The global economic situation has also dampened oil demand growth," analysts at research group JBC Energy said in a market note on Friday.
This week saw both the International Energy Agency and OPEC cut their oil demand forecasts, causing crude prices to drop.
Despite the demand outlook, US banking titan Goldman Sachs on Thursday forecast that Brent crude should hit about $130 a barrel within a year.
Prices in London closed up almost three dollars on Thursday, buoyed by a wave of market euphoria over a coordinated effort by five central banks to provide US dollars to cash-squeezed European lenders.
Sentiment got a shot in the arm after the European Central Bank announced it would, in cooperation with the central banks of the United States, Britain, Japan and Switzerland, provide three-month dollar loans.
Some European banks have run into difficulties in borrowing dollars amid concerns that contagion from the eurozone debt crisis could weaken the financial system.
The central bank announcement boosted the European single currency, making dollar-priced oil cheaper for euro-using buyers.