Oil closed at a record $93.53 a barrel on Monday as investors bet on another U.S. interest rate cut, the dollar struck new lows and Mexico briefly halted one-fifth of its oil production.
U.S. light, sweet crude closed up $1.67, while London Brent,which hit a record high $90, was over $89.
Oil prices have soared by more than a third since mid-August as a stand-off between Turkey and Kurdish rebels, dollar weakness, easing interest rates and winter supply fears have attracted a fresh wave of investment capital.
"Every new bullish factor pushes U.S. crude irrationally closer to $100 barrel," said SGCIB. But the bank went on to say: "Prices will fall if the FOMC does nothing."
The U.S. Federal Reserve's Federal Open Market Committee meets Tuesday and Wednesday. Wall Street is betting on another rate cut as the U.S. housing downturn deepens.
That expectation helped push the dollar to another record low against a basket of currencies, boosting the price of dollar-denominated commodities.
Central banks have poured billions of dollars into financial markets to ease a liquidity crisis. Much of that money has found its way into energy, commodities and emerging markets.
"In our view, implied volatility in crude oil options looks attractive... In addition, crude oil volume also looks attractive relative to volume in other asset classes," Merrill Lynch analysts wrote in a research note.
A strategist at Standard Life Investments said hedge funds had played a big part in driving oil prices towards $100.
"There's huge amount of speculation from hedge funds and others, they are all focused on the $100 barrel mark," said investment director Frances Hudson. "If volatility decreases significantly, they'd stop playing."
Also contributing to Monday's rally was news Mexico's state-owned oil company Pemex was shutting about 600,000 barrels per day of oil output due to bad weather in the Gulf of Mexico.
OPEC has shrugged off calls from importer nations to raise output, saying politics and speculation - not a supply shortfall - are to blame.
"I haven't any signal that there is any shortage of crude ... I believe a big portion of the oil price today is related to geopolitics and fear factors, and we cannot solve it," Qatari Oil Minister Abdullah al-Attiyah told reporters in Doha.
"Sometimes there is a shortage of oil products but not of crude. This is because of limitations of refinery (capacity). Consumers and producers should invest more in refining. We don't have a magic stick to solve this."
The possibility of a large-scale Turkish incursion into northern Iraq to root out Kurdish rebels is also keeping the oil market on edge. The tension has sparked worries of a broader conflict in the oil-rich Middle East.
"There remain concerns that oil market conditions are tightening and geopolitical tensions are also continuing to add a premium to oil prices," said David Moore, a commodities analyst at the Commonwealth Bank of Australia.
"The demand momentum for oil remains strong and supply is still constrained," Merrill Lynch said. "While U.S. oil demand is only running modestly above last year, demand in emerging economies has continued to grow on the back of a combination of subsidies (Middle East) and price caps(China/India)."