On Friday morning, crude futures were trading up 6%—putting Friday’s session on course to be the twelfth in less than three months in which oil gained 5% or more, according to The Wall Street Journal. The surge comes after Fed Chair Janet Yellen, accompanied by her three predecessors, expressed optimism about the U.S. economy in a panel discussion Thursday evening.

At the panel, which was held in New York, Yellen said that the U.S. economy was on a “solid course” with no clear bubbles forming. “I don’t see any particular reason to believe a recession is any more likely in 2016 than it was in 2015 or 2014,” she said.

On Friday morning, Federal Reserve Bank of New York President William Dudley added to the optimism with a speech advocating for a “cautious and gradual approach” to raising interest rate targets—an issue that has many traders on edge over the potential for the Federal Reserve to destabilize the economy by raising interest rates too quickly.

Oil prices are still down more than 20% from their levels last year, according to the Journal.