At the opposite extreme, this 1986 New York times article reports:

A team of geologists working for the Australian Government's Bureau of Mineral Resources reports in the journal Nature that it has discovered oil formed from the decayed remains of organisms that lived 1.4 billion years ago, when the earth was young. After the group drilled a 1,100-foot-deep test hole beneath the McArthur Basin in northern Australia, the oldest oil of its kind ever found bubbled to the surface.

Tiny amounts of oil as old as 3.2 billion years have been found more recently.