Oil prices closed lower on Monday after soft Chinese factory data raised worries about energy demand in the No. 2 economy, while record high Russian crude output suggested little easing in the global supply glut.
Also pressuring crude futures were lower prices for gasoline and ultra low sulfur diesel on expectations of higher U.S. refinery output as more plants emerge from their autumn maintenance cycle.
Brent crude futures, the global benchmark, traded down 79 cents at $48.78 a barrel at 2:33 p.m. EDT (1833 GMT). U.S. crude futures settled down 1 percent at $46.14 per barrel.
"High OPEC production, record-high production in Russia and weak China data are driving prices lower," said Carsten Fritsch, senior oil analyst at Commerzbank in Frankfurt.
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Early in the session, oil saw some support as the dollar came under pressure from data showing a fourth straight month of declines in October in U.S. manufacturing activity.
U.S. crude briefly traded in positive territory, with traders citing market intelligence firm Genscape's estimate of a decline of more than 400,000 barrels in inventories at the Cushing, Oklahoma delivery point for U.S. crude.
"In any event, the specter of significant slippage in Chinese oil consumption remains as an important background bearish consideration in our view within a market that is still very much oversupplied," said Jim Ritterbusch at Chicago-based oil consultancy Ritterbusch & Associates.
China's factory activity fell for an eighth straight month in October, a survey showed, pointing at continued sluggishness in the world's second-largest economy.
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Oil prices have tumbled by more than half since June last year on a global supply glut. Worries about the glut were fed on Monday, when Russia reported that its October oil production hit a post-Soviet record of 10.78 million barrels per day.
The data reflected Russia's strategy of defending its market share as rivals from the Gulf start supplying Moscow's traditional markets.
Last week, a Reuters survey showed sector analysts expected oil prices to remain weak next year as OPEC will likely stick to its stance of maintaining record-high production when it meets on Dec. 4.
OPEC member Iran is moving toward ramping up oil production and exports to Western consumers after starting decommissioning work on uranium enrichment under a nuclear deal struck with world powers in July.