On Wednesday oil prices traded lower as renewed fears over global demand and high stock levels hampered a rally that pushed up prices by about 19 percent over the past four sessions.
The recent rebound was spurred by hopes that prices may have hit a bottom. However, weak data from key consumer China has revived demand concerns, dragging on oil prices.
Estimates by industry group American Petroleum Institute that U.S. crude stockpiles rose more than 6 million barrels last week also helped drive prices lower on Wednesday.
Brent crude was 50 cents lower at $57.41 a barrel by 0336 GMT (10.36 p.m. EST), after gaining almost 6 percent on Tuesday and off a near six-year low of $45.19 reached in mid-January.
U.S. crude was down 95 cents at $52.10 a barrel. The contract settled up 7 percent in the previous session, after trading at as high as $54.24 earlier in the day - more than $10 above than a near six-year low of $43.58 reached last week.
On Tuesday oil major BP and top Chinese offshore energy producer CNOOC Ltd said they would deepen capital investment cuts this year to adapt to lower oil prices.
The outlook for oil demand has also been muddied by recent data showing China's services sector grew at the slowest pace in six months in January.
However, a number of analysts say lower oil prices will spur economic growth, which will boost demand for commodities including oil.
"Low oil prices and cheap money will lead to stronger global economic growth and much stronger oil demand than conventional wisdom would suggest," PIRA Energy told Reuters.
It forecasts global oil demand to grow by 1.5 million barrels per day in 2015, but warns the current supply surplus will overwhelm demand for the next six months.
A U.S. refinery strike at nine plants with about 10 percent of the country's refining capacity was set to go into its fourth day, after Royal Dutch Shell Plc failed to agree with union leaders over a new wage contract for refinery workers.
