Oil traded lower on the Chinese economic data. The Chinese preliminary Markit/Caixin manufacturing Purchasing Managers' Index (PMI) decreased to 47.1 in August from 47.8 in July, missing expectations for a decline to 47.7, and hitting a 77-month low.
Concerns over the global oil oversupply also weighed on oil prices.
Market participants are awaiting the release of the number of active U.S. rigs later in the day. The number of U.S. active oil rigs rose last week. The oil driller Baker Hughes reported that the number of active U.S. rigs rose by 2 rigs to 672 last week. It was the fourth consecutive increase.
WTI crude oil for October delivery declined to $40.11 a barrel on the New York Mercantile Exchange.
Brent crude oil for October decreased to $45.88 a barrel on ICE Futures Europe.