Oil prices dropped to near $81 a barrel Tuesday in Asia, the Associated Press reported. Benchmark crude for April delivery was down 68 cents to $81.19 a barrel at late afternoon Singapore time in electronic trading on the New York Mercantile Exchange. The contract rose 37 cents to settle at $81.87 on Monday. In other Nymex trading in April contracts, heating oil fell 0.53 cent to $2.10 a gallon, and gasoline dropped 1.74 cents to $2.272 a gallon. Natural gas was up 3.1 cents at $4.558 per 1,000 cubic feet. In London, Brent crude was down 69 cents at $79.78 on the ICE futures exchange.