New York's main futures contract, light sweet crude for delivery in June, surged higher throughout the trading session, hitting $114.18 a barrel just minutes before the market closed, the highest peak since September 22, 2008.
The West Texas Intermediate contract finished at $113.93 a barrel, up $1.07 from Thursday's closing.
"The two things that are very positive for oil are a weak dollar and a strong stock market and over the last few weeks we are getting both," said Adam Sieminski at Deutsche Bank.
The price of the New York benchmark climbed 6.7 percent over the month of April, and about 25 percent since the beginning of the year.
April was the eighth consecutive month of gains for WTI, Commerzbank analysts noted.
In London, Brent North Sea crude for June delivery was up 87 cents at $125.89 in electronic trading.
The financial markets in London were closed Friday in observance of the royal wedding of Prince William and Kate Middleton.
Quickening inflation in the 17-nation eurozone raised expectations Friday of an interest rate hike by the European Central Bank, boosting the euro against the dollar.
"The dollar is very weak and that relationship between a weaker dollar and stronger commodity prices, especially oil, is a powerful one," Sieminski said.
A weaker dollar encourages demand for dollar-priced oil from buyers using stronger currencies.
Eurozone inflation rose to 2.8 percent in April from 2.7 percent in March, according to a first estimate on Friday from the European data agency Eurostat.
April was the fifth month running in which inflation was above the ECB's 2.0 percent target.
Inflation, led by surging energy and commodity prices, prompted the ECB to lift its benchmark interest rate this month to 1.25 percent, its first hike in nearly three years.