Benchmark crude for June delivery was down $2.60, or 2.7 percent, to $93.79 a barrel in morning trading on the New York Mercantile Exchange.
Since oil is traded in dollars, a stronger dollar makes crude and other commodities less appealing to investors with other currencies.
On Friday the euro was down to $1.2947 from $1.3041 late Thursday in New York. The dollar also gained on the Japanese yen and was trading at 101.92 yen on Friday, after breaking above 100 yen on Thursday for the first time since April 2009.
The Organization of Petroleum Exporting Countries said it produced 30.5 million barrels of oil a day in April, the most since November. The group said global supplies increased 450,000 barrels a day. Production from non-OPEC nations like the U.S. is also on the rise at a time when supplies are ample and mixed global economic data raise questions about demand.
OPEC said it expected global oil use to be "much higher" in the second half of the year, but warned that the struggles of the eurozone and possible lower growth in China could hurt demand.
"A fragile recovery in the global economy has been visible since the beginning of the year, but momentum has started slowing again and growth risks are skewed to the downside," OPEC said in its monthly report on the oil market.
The national average for a gallon of gasoline rose a penny on Friday, to $3.56. It's about 4 cents higher than week ago, but 18 cents lower than the same time last year.
Brent crude, a benchmark for many international oil varieties, was down $2.41, or 2.3 percent, to $102.06 a barrel on the ICE Futures exchange in London.
In other energy futures trading on Nymex:
-- Wholesale gasoline fell 6 cents to $2.83 a gallon.
-- Heating oil lost 7 cents to $2.86 a gallon.
-- Natural gas fell 1 cent to $3.96 per 1,000 cubic feet.
Pablo Gorondi in Budapest and Pamela Sampson in Bangkok contributed to this report.
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