US oil futures climbed 81 cents to $48.35 a barrel on Friday, their highest closing level in more than three weeks, as dealers focused on the likelihood of Opec trimming output and a short cold spell in the US Northeast.
Talk that Opec is leaning toward reining in production ahead of the second quarter has been compounded by revised forecasts for a tighter-than-expected market this year.
"Oil market fundamentals remain extremely solid," SG Commodities said in a report. "Demand continues to rise at a sustained speed. Supply remains under the strict control of Opec."
While a healthy 8.5 percent year-on-year surplus in US crude oil inventories should soothe any concerns about short-term market tightness, dealers still worry that further builds could prompt tightening measures from Opec.
The Organisation of the Petroleum Exporting Countries (OPEC) meets on March 16 in Iran to plot second-quarter policy.
The market has also been supported by chily temperatures in the heating-oil consuming US Northeast, which should give a fillip to winter demand as the season winds down.
Attention will soon shift to the US summer driving season starting in May. Gasoline stocks rose last week to their highest level since 1999, helping defuse concerns that tight supplies could cause a springtime price spike.
Speculative hedge funds, whose participation in the market has climbed swiftly in recent years, increased their long positions in US crude futures slightly to 31,628 lots in the week ended February 15 in a bet prices would rise.