By Timothy Puko 

NEW YORK---U.S. oil prices flip-flopped around unchanged Thursday on dueling trends of tight inventories and weak demand.

Light, sweet oil for October delivery traded up eight cents, or 0.1%, to $93.53 a barrel on the New York Mercantile Exchange. Brent prices fell 50 cents, or 0.5%, to $101.78 a barrel on the ICE Futures Europe.

The U.S. benchmark had pushed down toward its low price for the year in early-morning trading. Weak demand signs, especially from disappointing manufacturing output from China, weighed on both U.S. and international prices.

That changed in the U.S. market as the floor opened. Strong spot buying caused prices to surge, said Andy Lebow, senior vice president for energy derivatives at Jefferies Bache LLC.

It fits in with a long-standing pattern of refineries draining supply from the Cushing, Okla., hub. Prices climbed in the prior session, too, on the same trend. Wednesday's stockpile update from the U.S. Energy Information Administration showed crude-oil stockpiles had decreased last week by 4.5 million barrels, five times more than expected.

"You're just seeing a continuation of the tight cash market," Mr. Lebow said. "The delivery point is very tight."

Front-month September reformulated gasoline blendstock, or RBOB, rose 0.42 cents, or 0.2%, to $2.7084 a gallon. September diesel edged up 0.68 cent, or 0.2%, to $2.8190 a gallon.

Write to Timothy Puko at timothy.puko@wsj.com

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