Bridge workers were forced to close one of the northbound lanes on the bridge after the spill occurred at 12.15pm.
The incident caused vehicles heading into Fife to bank up along the A90 as far south as the M9 spur.
A Forth Estuary Transport Authority spokesman said: “For safety and because oil can damage the asphalt on the bridge, it was essential that we cleaned it up as soon as possible.”
The bridge was reopened about 2.40pm.