Saudi Arabia is likely funding ISIL and the oil that ISIL sells is moving through Turkey. The Saudis want Assad out and Iran's influence in Syria contained.
In June 2014, Steve Clemons wrote in the Atlantic reported that Saudi Prince Bandar (Sunni) created a covert operation to help ISIL to expand into Syria from Iraq:
...two of the most successful factions fighting Assads forces are Islamist extremist groups: Jabhat al-Nusra [al-Qaeda in Syria] and the Islamic State of Iraq and Syria (ISIS), the latter of which is now amassing territory in Iraq and threatening to further destabilize the entire region. And that success is in part due to the support they [ISIL] have received from two Persian Gulf countries: Qatar and Saudi Arabia.
Qatar did not deny they fund both al-Qaeda groups, ISIL and Front, but they told Steve Clemons of the Atlantic that ISIL is a covert project of Saudi Arabia's Prince Bandar.
http://www.dailykos.com/story/2014/09/16/1330029/-Saudis-Lobbied-John-McCain-Lindsey-Graham-to-sell-War
Turkey
Western intelligence officials say they can track the Islamic State oil shipments as they move across Iraq and into Turkeys southern border regions. Despite extensive discussions inside the Pentagon, US forces have not attacked the tanker trucks, though a senior administration official said Friday that remains an option.
In public, the administration has been unwilling to criticize Turkey, which insists it has little control over the flow of foreign fighters into Iraq and Syria across its borders or the flow of oil back out.
http://www.bostonglobe.com/news/world/2014/09/13/seeks-turkey-help-starve-islamic-state-oil-revenue/IQIx3EPqamJ4iMfwEhQ7wI/story.html