SINGAPORE, Oct 27 (Reuters) - Oman crude futures on the Dubai Mercantile Exchange continued to weaken on Thursday, as the market's attention shifted to Saudi Arabia's official crude selling prices due out next week. Early expectations from the market point to a possible cut to the selling price of the lightest grades to Asian customers due to a weak naphtha market. The flagship Arab Light grade could edge up to new highs on the back of a firm Dubai backwardation, while the medium and heavy grades could benefit from strong fuel oil cracks, traders said. * DUBAI DIFFERENTIAL - Dubai has set its official differential to Oman futures OQc1 for January at a discount of 65 cents per barrel, the Dubai Department of Petroleum Affairs said on Thursday. The differential will be applied to the average of daily settlements for the front month January Oman contract at the end of November to set Dubai's official selling price (OSP) for January-loading crude. * TRADES - Phibro bought four Dubai partials from Unipec at $106.90-$107.30 a barrel. * OMAN ASSESSMENTS - December Oman traded on the DME was valued at a premium of $1.67 to Dubai swap quotes by 0830 GMT, using the settlement price for DME futures, the ICE one-minute marker for Singapore and the Brent-Dubai EFS as calculated by Reuters. This is down from a value of $2.90 in the last trading session on Tuesday. * EFS - Front-month Brent/Dubai Exchange of Futures for Swaps (EFS) for December fell 53 cents to the previous session at $5.15 a barrel. * MARKET NEWS - Royal Dutch Shell Plc (RDSa.L: Quote) will restart the third crude distillation unit (CDU) at its Singapore refinery within the next day or two, just under a month after a blaze shut the plant, industry sources said on Thursday. - Royal Dutch Shell Plc (RDSa.L: Quote) and Norway's Statoil reported big jumps in profits on Thursday, driven mainly by higher oil and gas prices with help from increased production. - OPEC-member Qatar has joined Mexico in taking out an insurance policy against falling oil prices next year, hedging some of its oil for 2012 as both nations adopt a cautious view about the global economy, the Financial Times reported on Thursday. - Vietnam-Russia oil joint venture Vietsovpetro will produce 6.0-6.1 million tonnes a year of crude starting in 2012, slightly lower than expected output this year, a senior company official said on Thursday. * REFINERY MARGINS - Complex processing margins for Dubai in Singapore were around $10.38 per barrel, up from an average of the last five days of $8.89, Reuters data show. Over the last year, the average margin has been around $8.01 per barrel. * CRACK SPREADS - Fuel oil's November crack narrowed 22 cents to a discount of $3.45 a barrel to Dubai crude. - Gas oil's November crack climbed 74 cents to a premium of $19.28 a barrel to Dubai crude. - The naphtha CFR Japan front-month crack gained $1.29 to a discount of $13.58 a barrel to Brent. * OUTRIGHT PRICES - December ICE Brent LCOc1 fell to $110.54 a barrel by 0830 GMT, down $1.06 from the same time a day earlier. - December Oman OQc1 fell 92 cents to settle at $107.04. (Reporting by Francis Kan; Editing by Michael Urquhart)

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