New York light crude shed $2.17, 3.2%, to $64.76 a barrel, while Brent crude shed $2.62, or 3.7%, to $68.60.
Prices had been pushed higher by fears that the cyclone would dent output from oil producers Oman and Iran, though, it eventually weakened into a rain storm.
At the same time, analysts are worried high rates will slow the world economy.
Phil Flynn, an energy analyst at Alaron Trading, said that the market was running out of reasons to believe that oil prices would continue to climb.
However, other analysts are predicting the problems in Nigeria, where workers have been kidnapped and production facilities damaged, could underpin prices and stop them falling too far.
On Friday, Lehman Brothers raised its estimates for oil prices in 2007 and 2008.
The Wall Street brokerage said it expects an average price of $62 a barrel this year, and a price of $55 a barrel in 2008.
Cyclone Gonu was the most powerful storm in the Gulf for 60 years.
Thousands of residents were evacuated from Oman's coast, and hundreds were also moved from the Iranian coast.