Oil prices fell below $81 a barrel Monday in Asia, the Associated Press reported. Benchmark crude for April delivery was down 40 cents to $80.84 a barrel at midday Singapore time in electronic trading on the New York Mercantile Exchange. The contract rose 60 cents to settle at $82.09 on Friday. In other Nymex trading in April contracts, heating oil was down 0.2 cent at $2.092 a gallon, and gasoline dropped 0.4 cent to $2.251 a gallon. Natural gas declined 4.3 cents to $4.357 per 1,000 cubic feet. In London, Brent crude was down 40 cents at $78.99 on the ICE futures exchange.