Prices lost $1.31 a barrel during the day's trading session.
A debt-ceiling debate in Washington -- with an Aug. 2 deadline looming before the country defaults on its obligations -- and the European sovereign-debt crisis were the chief reasons oil prices' retreated, Matt Smith, an oil analyst with Summit Energy in Kentucky, told MarketWatch.com.
Other energy products traded lower Monday as well.
Gasoline dropped 3 cents to settle at $3.10 a gallon.
Home heating oil lost 4 cents to $3.08 a gallon.
Natural gas was basically flat, settling at $4.55 per million British thermal units.
At the pump, the average price for a gallon of regular unleaded gasoline Monday was 3.676, up from Friday's average price of $3.667, AAA reported.