Oil futures posted a weekly loss of more than 8% on Friday, pressured by ongoing worries about a global glut of supplies, a lack of significant production cuts and some strength in the U.S. dollar on the heels of the U.S. jobs report.

Meanwhile, futures prices for gasoline finished under $1 a gallon for the first time since late 2008. Analysts attributed the drop to a purge of winter blends of the fuel.

March West Texas Intermediate crude CLH26, shed 83 cents, or 2.6%, to settle at $30.89 a barrel on the New York Mercantile Exchange, pulling back from an earlier high of $32.45. It spent much of the session seesawing between losses and gains after the jobs report. For the week, prices suffered a loss of roughly 8.1%.

April Brent crude UK:LCOJ6 on London’s ICE Futures exchange lost 40 cents, or 1.2%, to $34.06 a barrel, ending more than 5% lower on the week.

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This has been “a tricky week for crude-oil trading because the downside move in the U.S. dollar was fast and intense,” said Richard Hastings, macro strategist at Seaport Global Securities.

Oil prices caught a bid recently on the U.S. dollar downdraft, “but this is a dangerous game,” he said. “If the USD declines too much, then the Bank of Japan and the [European Central Bank] will respond with more aggressive stimulus and accommodation measures to pressure their currencies lower.” That would contribute to gains for the greenback.

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Already, the dollar is “starting to snap a bit higher,” he said. The ICE U.S. Dollar Index DXY, -0.17% was up roughly 0.6% in Friday trading in reaction to the monthly jobs report. A stronger dollar can make dollar-denominated commodities more expensive for foreign buyers.

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U.S. Labor Department report showed that the domestic pace of hiring tapered off in January, but wages rose sharply and the unemployment rate dipped below 5% for the first time since 2008.

“Now there’s some evidence that the US economy is beginning to decelerate after a very long, complex expansion from about 2012,” said Hastings. “Oil prices will come under pressure again due to economic demand concerns.”

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Overall, oil’s fundamentals remain weak due to a supply overhang, as major producers have refused to cut output despite prices falling sharply for nearly two years.

In a report Friday, Wood Mackenzie said there has been “minimal production shut-in so far in this [price] downturn,” with the decline equivalent to less than 100,000 barrels a day or 0.1% of global production.

Read:Oil output barely dented despite crude’s plunge

Meanwhile, data on the number of active U.S. oil-drilling rigs from Baker Hughes US:BHI Friday revealed a seventh straight weekly decline. The count fell by 31 to 467.

Sub-$1 gasoline futures

Back on Nymex, gasoline prices ended below $1 a gallon for the first time since late 2008.

Earlier this week, Tom Kloza, global head of energy analysis at the Oil Price Information Service, told MarketWatch that “the gasoline that is in the U.S. system now is ‘perishable’.”

“There is a bit of a ‘grand negative finale’ in the way that refiners dump it in midwinter to make way for the spring blends” of gasoline, he said.

This is the “last purge” of the gasoline market, he said, as he believes prices will rally into March and April.

March gasoline US:RBH6 declined by 3.6 cents, or 3.5%, to 99.27 cents a gallon, for a weekly loss of more than 12%. March heating oil US:HOH6 lost 2.2 cents, or 2%, to $1.059 a gallon—about 1.8% lower for the week.

March natural gas US:NGH16 tacked on 9.1 cents, or 4.6%, to $2.063 per million British thermal units, but ended about 10.2% lower for the week.