US crude for November delivery was down 15 cents on the day at $82.51 a barrel at 1748 GMT. In London, ICE November Brent crude fell 16 cents to $83.87 a barrel.
The dollar grew stronger against other currencies on Monday. That pressured oil prices, because a stronger dollar makes crude, priced in dollars, less attractive to investors who buy it with other currencies. In the past week, crude prices have stayed above $80 a barrel as traders set aside the reality of plentiful supplies and weak demand for oil and gas to focus on the ups and downs of the dollar versus the euro.
Analysts and traders said the fillip to prices caused by expectations of further quantitative easing in the United States, which helped raise US crude as high as $84.43 a barrel last week, might have run its course as the dollar firmed on Monday.
Oil was relatively steady on the news that China, the world's largest energy user according to the International Energy Agency, had raised the required reserves of its four leading state banks to drain cash from the economy.
Reacting to the news, Amrita Sen, a commodities analyst at Barclays Capital in London, said the impact on China's energy demand would be muted.
"Given how energy intensive the Chinese economy is, even with some soft landing we do not expect this to change," Sen said.
The market will seek further clues to developments in the global economy from the release of the minutes for the last US Federal Reserve meeting on Tuesday, China trade data on Wednesday and US retail sales for September on Friday.
Prices took some support as a strike at France's top oil port of Fos-Lavera continued into a 15th day on Monday. The nearby La Mede oil plant said over the weekend it had half idled its capacity and will fully shut down in a couple of days because of the disruption to supplies.
Workers at Petroplus's 154,000-barrel-per-day Petit Couronne refinery in northern France also started a rolling 24-hour strike over pensions, blocking fuel supplies and
reducing production.
Disruptions to the supply of gasoline and diesel in France have boosted oil product prices and helped underpin the broader market, but some analysts cautioned that lower refinery
operations could ultimately weigh on crude prices as less is processed.
