Benchmark West Texas Intermediate crude for June delivery fell 87 cents to finish at US$95.17 a barrel on the New York Mercantile Exchange.
The U.S. dollar has risen in recent days against the euro and last week passed the 100-yen mark for the first time in four years. Since oil is traded in dollars, a stronger dollar makes crude and other commodities less appealing to investors with other currencies.
"This, like the stock market, ends up pulling a lot of money out of commodities and into more reliable risk," said Carl Larry, president of Oil Outlooks and Opinions, a research analysis firm.
An increase in OPEC's output, which grew by 280,000 barrels to 30.46 million barrels a day in April compared with March, also helped drag down prices by boosting concerns about excess supply.
And weak refining data from China further undercut crude. Government statistics showed China's refining output in April was the lowest since last August.
Brent crude, which is a benchmark for many international oil varieties, was down $1.09 to end at US$102.82 a barrel on the ICE Futures exchange in London.
In other energy futures trading on the Nymex, wholesale gasoline fell four cents to finish at US$2.82 a U.S. gallon (3.79 litres), heating oil lost two cents to end at US$2.89 a gallon and natural gas rose two cents to finish at US$3.93 per 1,000 cubic feet.
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