U.S. oil prices fell below the $18-a-barrel mark.

West Texas intermediate, the key U.S. crude, lost 8 cents to $17.98 a barrel for March delivery on the New York Mercantile Exchange. The benchmark domestic crude last finished below the $18 level on Dec. 31, when it closed at $17.94 a barrel. During Thursday’s trading, West Texas intermediate had fallen as low as $17.75 a barrel before refiners and other oil users began buying the crude. On the U.S. Gulf Coast market, where oil is sold to the highest bidder, the West Texas crude fell 20 cents to $17.95 a barrel.