Benchmark crude fell 25 cents Friday to end the week at $101.56 per barrel in New York.
Brent crude, which is used to price foreign oil varieties that are imported by U.S. refineries, rose 32 cents to finish at $113.06 per barrel in London.
Oil prices jumped above $100 a barrel this week on growing tension in the Persian Gulf.
Iran has threatened to block the Strait of Hormuz, if the U.S. and other nations enforce more economic sanctions against Iran because of its nuclear program.
The strait provides the only way out of the Persian Gulf for oil tankers carrying one-sixth of the world's exports. Experts say it's unlikely that Iran could follow through with its threat, but fears of military action could slow shipments at a time when global demand is higher than ever.
In other energy trading, heating oil rose by 3 cents to finish at $3.07 per gallon and gasoline futures rose by 2 cents to end at $2.75 per gallon. Natural gas rose by 8 cents to finish at $3.06 per 1,000 cubic feet.
Gasoline prices hit an average of US$3.35 a gallon, the highest ever for this time of year.
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