SINGAPORE, Sept 6 (Reuters) - The increase in October official selling prices (OSPs) by Saudi Arabia and Abu Dhabi were mostly in line with expectations and firm product margins are expected to support demand this month. Demand expectations have risen after a poll showed this week that China's biggest refineries are set to increase the volume of crude oil processed in September, reversing cuts in the previous two months, after the startup of a new unit offsets production drops at other plants. OSPS: - Saudi Aramco raised its October OSP for Asia on all grades except Arab Heavy. It raised the OSP for lighter grades by more than a dollar, with the Arab Super Light rising by more than $2. The Arab Heavy grades were cut by 40 cents. - Abu Dhabi National Oil Co. has raised the August retroactive OSP for its key Murban crude by $9.90 from July to $111.65 a barrel from $101.75 a barrel. *MARKET NEWS - A Russian firm has decided to stop verifying safety and environmental standards for one of Iran's biggest shipping groups, a letter showed, the latest international company wary of being caught up in Western sanctions - Singapore onshore middle distillates stocks slipped to their lowest in five weeks while fuel oil and light distillates inventories rose in the week ended Sept. 5, state trade agency International Enterprise (IE) data showed on Thursday. CRUDE Price Prev Change OCT DME Oman diff to Dubai swaps OCT Brent 114.23 113.94 +0.29 OCT Dubai 111.18 110.64 +0.54 NOV DME Oman 112.25 111.79 +0.46 OCT Brent/Dubai EFS 3.05 3.30 -0.25 PRODUCT CRACKS OCT fuel oil crack -5.74 -5.58 -0.16 OCT gasoil crack 18.83 19.16 -0.33 OCT naphtha crack -5.56 -6.11 +0.54 COMPLEX REFINERY MARGINS Today +7.82 Last 5 days +9.14 Last 365 days +7.37

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