But in the absence of fiscal tightening that significantly cuts the non-oil and gas fiscal deficit, a severe and sustained drop in the oil price would have a damaging impact on the Russian economy and public finances and would likely lead to a downgrade, Fitch warned.

FORBES: Is A Russia Credit Downgrade Coming?

An EU embargo of Iranian crude would halt around 600, 000 barrels a day of imports, hitting Europe's refiners hard and further tightening markets and inventories, putting upward pressure on oil-futures prices, the International Energy Agency has said.

WSJ: Oil's Tug of War Is Poised to Continue

Oil prices fell something like 15% in the third quarter as markets began to price in the prospects for substantially slower growth across the developed world and tightening in the fast-growing emerging markets. (Read Oil Down More Than 15% This Quarter As Sector Stocks Price In Recession).

FORBES: Halliburton's Resilience: Record Revenue, Op. Income Despite Tumbling Oil Prices