Analysts said investors were also monitoring a storm gathering in the Gulf of Mexico that threatens to disrupt oil supply in the southern United States.
New York's main contract, light sweet crude for delivery in October, lost 18 cents to USD 88.75 per barrel. Brent North Sea crude for October delivery dipped 17 cents to USD 114.12.
"The US jobs data is coming out tonight, and there is a likelihood that prices will stay in a tight range," said Ker Chung Yang, a Singapore-based commodity analyst at Phillip Futures.
Markets remained jittery before the release of US nonfarm payrolls data later Friday, which will indicate whether the labour market in the world's biggest economy is showing any signs of improvement.
Meanwhile, oil majors including BP, ExxonMobil and Royal Dutch Shell have started evacuating workers from their rigs in the Gulf of Mexico ahead of a storm that forecasters say has a 70 per cent chance of becoming a tropical cyclone.