US crude oil for November fell 69¢ to stand at $80.56 today, a decrease of 2.9% since Friday.
Crude oil prices touched $80.30 on 8 October, the lowest price since the beginning of the month, after reaching a five-month high of $84.43 a day earlier. December ICE Brent fell 65¢ to stand at $81.80.
The US central bank is to ease its monetary policy even further in a debt purchase programme.
Société Générale head of oil market research Mike Wittner told Reuters: “The second round of quantitative easing, which had been progressively bullish for oil over the course of September and into early October, ran out of steam as a driver for prices, at least for the time being.”
Members of the US Federal Reserve will meet on 2 November, and are expected to reveal details of stimulus moves.