Dubai: Abu Dhabi National Oil Company (Adnoc) has set the October retroactive official selling price (OSP) of its main Murban crude at a record $81.80 a barrel, up $3.25 from September, Adnoc said yesterday.

The rise came even though Adnoc lowered the grade's premium to Dubai by 51 cents a barrel to $4.68.

Adnoc, the largest oil production firm in Opec-member the UAE, set its Upper Zakum grade at an all time high of $77.80 a barrel, a premium of 67.8 cents to Dubai.

Upper Zakum is usually set at a discount to Dubai. Prices for the grade in September and October were the first to carry a premium to Dubai since September 2005.

The surge in premiums came after refiners snapped up spot cargoes ahead of oilfield maintenance that was expected to cut Abu Dhabi crude supplies by some 600,000 barrels per day.

The UAE is the world's sixth-largest oil exporter. Output stood at around 2.57 million bpd in October, a survey showed.