Oil prices climbed slightly on Monday as traders reacted to a pick-up in China's services industry ahead of Beijing's leadership transition and the US presidential election.
New York's main contract, light sweet crude for delivery in December, rose 17 cents to $85.03 a barrel.
Brent North Sea crude for December gained 14 cents to $105.82 a barrel in late London deals.
Prices were "lifted by China's non-manufacturing PMI data, which showed an improvement," trading group IG said in a report.
It added that the figures backed up analyst consensus opinion that China, the world's biggest energy consumer, had come to the end of its slowdown, supported by last week's data showing an increase in manufacturing output.
"This week is all about changes in leadership and policy meetings which are likely to keep traders firmly sat on the sidelines," IG said.
US President Barack Obama and challenger Mitt Romney go into Tuesday's election neck and neck with markets waiting to see who will be the next leader of the world's biggest economy and oil consumer.
Obama had a lift on Friday when the Labor Department said 171,000 new jobs were created in October, well above forecasts.
China begins its power transition on Thursday, fuelling market sensitivity as traders monitor developments in the Asian powerhouse.