Oil prices tumbled nearly four percent to settle below 72 U.S. dollars on Tuesday as investors eye another increase in crude stockpiles. The U.S. Energy Department is set to release the latest fuel inventory report on Wednesday, and the market expected the crude oil stocks to rise for a second week. Total oil inventories are already at the highest since at least 1990, according to government data. Concerns about weak demand has send crude futures traded in New York falling for seven percent this month. Light, sweet crude for October delivery fell 2.78 dollars, or 3. 7 percent, to settle at 71.92 dollars a barrel on the New York Mercantile Exchange. Brent crude for October delivery fell 2.13 dollars to 74.47 dollars a barrel on the International Futures Exchange in London. 