Oil tumbled for a third straight week as crumbling equity markets across the globe stoked concern about a slowdown in energy demand growth Friday\u2019s 0.4 percent gain New York-traded futures wasn\u2019t enough to halt a 2.2 percent decline for the week. Eight of every 10 stocks in the S&P 500 were in retreat as a cavalcade of negative news killed investors\u2019 appetites for risk. A closely watched tally of U.S. rig activity indicated drillers intend to step up crude output. \u201cOil is dropping because of more concern about what\u2019s happening in the stock market,\u201d said Phil Flynn, an analyst at Price Futures Group. \u201cThe high volatility in the stock market and fear selling in other markets is spilling over into the oil complex.\u201d Crude shed almost 8 percent of its value so far this month, wiping out all the gains of August and September. Faltering confidence in the strength of the global economy comes as swelling American oil stockpiles spark fears about a re-emergence of a price-killing glut. U.S. efforts to isolate Iran and its crude output, as well as spiraling Venezuelan production, haven\u2019t been enough to serve as a geopolitical counterweight to the selloff. \u201cEquities have resumed their decline and that is dragging oil down again,\u201d said Giovanni Staunovo, an analyst at UBS Group AG. \u201cThe market is showing how much the sentiment has shifted once again. A month ago it was bullish, now it\u2019s bearish again.\u201d West Texas Intermediate for December delivery added 26 cents to settle at $67.59 a barrel on the New York Mercantile Exchange. The futures closed above the 200-day average for the first time in four sessions. Total volume traded was about 16 percent below the 100-day average. Brent for December settlement added 73 cents to settle at $77.62 on the London-based ICE Futures Europe exchange. Prices were down 2.7 percent for the week. The global benchmark crude traded at a $10.03 premium to WTI for the same month.