Benchmark U.S. oil gave up 20 cents to finish at US$96.81 per barrel in New York. The six-day drop is the longest for U.S. oil since July 2011.
Prices have been declining in reaction to new doubts about Europe's ability to fix its economy and disappointing jobs growth in the U.S. And as slowing economies temper the demand for oil, the amount of crude in storage rises.
On Wednesday, the Energy Information Administration said that increased oil imports and weaker domestic demand for petroleum helped boost the nation's oil supply last week to 379.5 million barrels, the highest since 1990.
The U.S. Commerce Department also said U.S. wholesalers increased their stockpiles more slowly in March, hinting at a slowdown at the nation's factories.
"There's just an inherent mood out there for caution," said Peter Donovan, a broker with Vantage Trading.
Saudi Arabia also is boosting supplies in an effort targeted toward pushing world oil prices lower. And Iran is scheduled to meet in two weeks with several other countries including the U.S. to talk about its nuclear program. That has eased fears of a protracted standoff that could slow oil shipments out of the Middle East.
At the pump, retail gasoline prices fell by more than a penny to a national average of $3.75 per gallon, according to auto club AAA, Wright Express and the Oil Price Information Service. A gallon of regular unleaded has dropped an average of 19 cents in about a month. Gasoline is 21 cents cheaper than it was at the same time last year.
In Canada, the price at the pump averaged C$1.29 per litre, down from $1.348 per litre a month ago, according to price-watching website GasBuddy.com.
OPIS chief oil analyst Tom Kloza said that gasoline prices should gradually decline this summer. He estimates that the national average could slip as low as US$3.50 per gallon by the Fourth of July.
In other futures trading, heating oil added nearly a penny to finish at $2.9991 per gallon and wholesale gasoline rose by 2.97 cents to end at $3.0241 per gallon. Natural gas added 7.2 cents to finish at $2.465 per 1,000 cubic feet.
Brent crude, which sets the price for oil imported into the U.S., added 47 cents to finish at $113.20 a barrel in London.
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