Crude oil futures fell more than 1 percent on Friday, down for the sixth straight session, as worsening problems in Greece and Spain raised worries of contagion in the eurozone.
Oil futures fell on the drumbeat from global stock markets, which erased the year's gains as investors pared holdings for safe-haven assets such as gold, on growing concerns about the eurozone debt crisis.
On Wall Street, equities dipped after a messy opening-day trade for social networking darling Facebook failed to lift the spirits of investors.
U.S. gasoline futures bucked the day's trend in energy markets, gaining slightly after six days of losses and climbing above its 200-day moving average after falling below that level on Thursday for the first time since February.
Oil investors were cautious ahead of the G-8 summit this weekend where U.S. President Barack Obama was reported by Japanese news agency Kyodo to be seeking support for tapping the release of emergency oil reserves ahead of the European Union's July embargo of Iranian crude.
Obama will host the G-8 meeting at Camp David in Maryland.
Reversal of the Seaway pipeline was completed earlier this week and its first crude oil headed for Houston from Cushing, Oklahoma, is expected to flow by the weekend, according to owners Enterprise Products and Enbridge Inc
Anticipation of the landmark move, which was expected to help ease the glut in Midwest crude stockpiles, had reduced Brent's spread against U.S. crude in recent days, but on Friday, the spread widened, amid caution from analysts that impact of the reversal could be slow to hit the U.S. oil markets.
On the New York Mercantile Exchange, crude for June delivery, which expires on Tuesday, settled at $91.48 a barrel, falling $1.08, or 1.17 percent. For the week, it slid $4.65, or 4.84 percent, down for the a third in a row.
In three weeks, front-month U.S. crude has slumped $13.45, or 12.82 percent, the biggest three-week loss since the week to August 14, 2011, when prices dropped 14.54 percent.
In London, ICE July Brent crude settled at $107.14 a barrel, edging down 35 cents, or 0.33 percent, the lowest close for front-month Brent since the December 20, 2011 settlement at $106.73 and extending losses to a third straight week.
In three weeks, front-month Brent has fallen $12.69, or 10.59 percent, its biggest three-week drop since the week to May 20, 2011, when prices ended 10.72 percent lower.
July Brent's premium against U.S. July crude widened to $15.34, from $14.55 on Thursday, as Brent fell far less than U.S. crude.
NYMEX June heating oil fell 1.90 cents, or 0.67 percent, to settle at $2.83 a gallon, dropping for the third consecutive day. For the week, the contract fell 13.36 cents, or 4.51 percent, stretching weekly losses a third week.
In three weeks, front-month heating oil dropped 35.07 cents, or 11.03 percent, the biggest three-week loss since the week to May 8, 2011, when prices fell 11.94 percent.
NYMEX June RBOB gasoline settled at $2.8895 a gallon, up 1.13 cents, or 0.39 percent, snapping a six-day losing streak. However, for the week, the contract fell 11.13 cents, or 3.71 percent, biggest since the loss of 7.19 percent in the week to May 4. The loss followed a small gain of 0.84 percent in the week to May 11.
Hedge funds and big speculators cut their bullish bets on U.S. crude oil and options by 12,789 contracts, to 140,936, in the week to May 15, hitting the lowest level since late 2010, according to a weekly report from the U.S. Commodity Futures Trading Commission.
The number of oil drilling rigs in the United States rose 10 to 1,382 last week, the highest level in 25 years, according to a weekly report from oil services firm Baker Hughes.
U.S. petroleum consumption fell 0.3 percent in April from a year ago, to 18.549 million barrels per day and gasoline usage climbed for the third month in a row, the American Petroleum Institute said.
Iraq's oil exports from is southern ports have slipped by 170,000 bpd so far this month, according to shipping data tracked by Reuters, although Iraq hopes remain it will sustain shipments at April's record rate.
Gold rose more than 1 percent, on track for its largest two-day gain since October as investors consolidated their positions ahead of the weekend and amid a stronger euro.
U.S. stocks fell after a sloppy debut by Facebook Inc (FB) failed to brighten the mood on Wall Street. .
The euro rallied from a four-month low against the dollar as investors pared bets against the single currency after a more than 3 percent drop this month, but concerns about the eurozone were likely to keep it under pressure.
Copper fell for a third straight week, having lost 4.5 percent of its value over the past five days, on fears Europe's spiraling debt crisis and China's slowdown will erode demand for metals.
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