Benchmark oil for December delivery was down 75 cents to $85.53 a barrel at late afternoon Bangkok time in electronic trading on the New York Mercantile Exchange. The contract rose 23 cents to end at $86.28 per barrel in New York on Friday.
Forecasters say the massive storm system could blow ashore Monday across a wide swathe of the eastern seaboard, bringing with it the potential for massive flooding and widespread power outages.
"We're going to get some bad weather somewhere in the U.S. because of Hurricane Sandy and that's not good for demand," Carl Larry of Oil Outlooks and Opinions said in an e-mail commentary.
New York City, the nation's biggest city, is in the direct path of the storm and expected to bear its brunt.
Air, land and rail transportation was halted and hundreds of thousands of people have been ordered to evacuate.
The New York Stock Exchange and the New York Mercantile Exchange are shutting their trading floors in New York Monday, although trading will go on electronically.
While more than half a dozen refineries could be in the path of the storm, the U.S. is well-supplied with oil while demand for gasoline is down as large numbers of Americans remain unemployed and so don't drive to work.
Oil is down 13 percent since hitting $99 in mid-September.
In London, Brent crude, which is used to price international varieties of oil, fell 55 cents per barrel to $109.01.
In other energy futures trading in New York:
— Heating oil rose 0.6 cents to $3.082 per gallon.
— Wholesale gasoline rose 0.7 cents to $2.649 per gallon.
— Natural gas fell 0.1 cent to $3.391 per 1,000 cubic feet.