Brent crude futures for September fell 21 cents to $66.51 a barrel while US crude for August was down 28 cents at $59.93 a barrel, Reuters reported.
Both contracts last week posted their biggest weekly gains in three weeks on cuts in US oil production and diplomatic tensions in the Middle East.
Refineries in the path of tropical storm Barry continued to operate despite flood threats while the storm has slashed US Gulf of Mexico crude output by 73%, or 1.38 million barrels per day.
An unwinding of the risk premium from tropical storm Barry, lower oil demand forecasts and a lack of news from the Middle East may have led to a muted oil price reaction, Stephen Innes, managing partner at Bangkok-based Vanguard Markets, said.
China’s economic growth slowed to 6.2% in the second quarter from a year earlier, in line with analysts’ expectations, with demand at home and abroad faltering as the Sino-US trade war bites.
Still, China’s industrial output and retail sales beat forecasts, “suggesting that the economy in China is healthier than we previously been pricing,” said Michael McCarthy, chief market strategist at CMC Markets in Sydney.