The researchers' work began two years ago when Dr Misra, a heavy coffee drinker, left a cup unfinished and noticed the next day that the coffee was covered by a film of oil.
"I think it brings up the QE3 question again, but one data point will not be enough to convince the Fed about the need for further easing, " said Priya Misra, head of U.S. rates strategy research at Bank of America Merrill Lynch in New York.