New York's main contract, light sweet crude for September delivery, sank USD 1.13 to USD 90.70 a barrel while Brent North Sea crude for delivery in September eased 86 cents to USD 105.97.
Spain's ability to handle its finances is spooking investors this time amid worries that the country, the fourth largest economy in the eurozone bloc, would need a bailout.
The country was forced to pay borrowing costs above 7.0 per cent in a 10-year bond sale, a level considered unsustainable and that pushed Greece, Ireland and Portugal into asking for bailouts.
"The eurozone crisis has become the focus again," Singapore's DBS bank said in a commentary. "The market's main fear is that Spain may require a full bailout some time in the future," it said. Crude futures had soared in recent sessions, hitting two-month highs Thursday, as traders worried that rising tensions in the oil-rich Middle East will hamper supplies.