SINGAPORE, Sept 13 (Reuters) - Russian light sweet Sokol crude premium rose on Thursday to its highest in four months, reflecting strong demand for distillates-rich grades ahead of winter. * TENDERS - Russia's top oil producer Rosneft sold two 95,000-tonne cargoes of Sokol crude to South Korean refiners SK Energy and GS Caltex at premiums of between $7.40 and $7.60 a barrel to Dubai quotes, they said. The cargoes will load on Nov. 7-16 and 16-25. The deals could not be independently verified. * OSP - Malaysia's Petronas has reduced the Tapis crude price alpha factor for September liftings to $3.05 per barrel, the lowest in 17 months as refinery outages and abundant arbitrage supply have depressed spot premiums. The September Tapis alpha is down $1.95 from the previous month. The alpha factor is used to calculate the official selling price (OSP) of Malaysia's main export crude. Petronas also announced the differentials for Labuan, Miri Light, Dulang, Bintulu and Kikeh to dated Brent as it starts new price formulas for these grades from September to better reflect higher values for distillates-rich crude. * MARKET NEWS - South Sudan could produce at least 300,000 barrels per day of oil when it resumes full production, but that may take until mid-2013 because of damage caused during its border dispute with Sudan, an oil official said. CRUDE Price Prev Change OCT Brent 115.81 116.13 -0.32 OCT Brent/Dubai EFS DUB-EFS-1M 3.15 3.35 -0.20 PRODUCT CRACKS OCT fuel oil crack -5.87 -5.82 -0.05 OCT gasoil crack 18.84 18.92 -0.08 OCT naphtha crack -7.25 -6.24 -1.01 COMPLEX REFINERY MARGINS Today 8.81 Last 5 days 8.62 Last 365 days 7.36

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