The cost of hiring 1 million-barrel tankers to collect crude oil from Black Sea ports may snap a two- day drop because of congestion in Turkey's Bosporus Straits. Tankers making a round-trip through the straits face delays of 10 days, according to Istanbul-based Master Maritime Agencies Inc. Delays occur at this time of year in the Bosporus, a key route for oil exports from Russia, as reduced daylight hours require slower travel. “There are not many vessels available and lots of delays at the Bosporus,” said Luis Mateus, an analyst with shipbroker Riverlake SA in Geneva. Freight rates for suezmax tankers, which hold 1 million barrels, bound from Black Sea ports to refineries in the southern Mediterranean, last week rose 98 percent, their biggest gain in almost a year. The route fell 1.9 percent to 210.4 Worldscale points today, according to London's Baltic Exchange. Worldscale points are a percentage of a nominal rate, or flat rate, for more than 320,000 specific routes. Flat rates for every voyage, quoted in U.S. dollars a ton, are revised annually by the Worldscale Association in London to reflect changing fuel costs, port tariffs and exchange rates. Each flat rate assessment gives owners and oil companies a starting point for negotiating hire rates without having to calculate the value of each deal from scratch. A rental rate of 210.4 Worldscale points equates to about $99,340 a day for a typical Black Sea to Mediterranean voyage, according to a formula from Oslo-based shipbroker RS Platou AS and Bloomberg ship-fuel prices. Frontline Ltd., the world's biggest operator of supertankers, said Nov. 15 it needs $22,100 a day to break even on each of its 1 million-barrel tankers