Oil down more than 6 percent after US credit downgrade

Oil plunged to its lowest price of the year today on concerns about the slowing global economy and future demand for oil and gas.

Benchmark West Texas Intermediate crude fell $5.57, or 6.4 percent to settle at $81.31 per barrel on the New York Mercantile Exchange. That is the lowest settlement price of the year for crude, but it's still higher than the $71.63 per barrel low of the past 12 months. Oil hit that on Aug. 24 of last year, when a combination of disappointing economic news and abundant supplies drove down prices.

Brent crude, used to price many international varieties of crude, today fell $5.63, or 5.2 percent, to settle at $103.74 per barrel on the ICE Futures exchange in London.

Anxious traders pulled money out of oil and stocks and bought assets considered to be safer during times of economic uncertainty, such as Treasurys and gold.

Standard & Poor's on Friday cut the Triple-A credit rating for long-term U.S. government debt.