New York's main contract, light sweet crude for delivery in August fell 34 cents to $85.47 a barrel in the afternoon and Brent North Sea crude for August delivery shed 22 cents to $100.01.
Concerns about additional quantitative easing (QE) for the US economy came to the fore on Wednesday following the release of the minutes of the June 19-20 Federal Open Market Committee meeting, IG Markets said in a report.
"While a handful of Fed members acknowledge the need for QE the timing or actual breaking point for when this will happen is still unclear," the report stated.
"This lack of clarity and inaction saw investors fly to safe haven assets" like the US dollar, IG Markets' report added.
The euro fell to $1.2233 in early Asian trade from $1.2238 in New York late on Wednesday, dragging down oil prices as a stronger greenback made dollar-priced crude more expensive to traders using other currencies.
In the Fed minutes, several top policymakers urged the central bank to look at new tools to boost the US financial system as economic recovery in the world's largest oil consumer stuttered.
But it also laid bare divisions within the Fed over how much more the bank should do.