For some months now the Western media, which is essentially the PR department of London, Washington and Paris, has been informing its readers that ISIS gains a significant part of its revenue from oil.
Curiously, these stories have not reported on the destination of the smuggled oil. This piece in the New York Times from mid-November is a good example. The piece reports on hundreds of tankers and the millions of dollars being made but is curiously silent on who is buying the oil. This has been going on for months. There are multiple news reports in the Western media with the same strange silence about the purchaser of the oil.
Now that Russia has outed who the purchaser is  the US State Department is rushing into damage limitation mode. Russia’s allegations are “preposterous and kind of ridiculous”.  And the amount going to Turkey is “insignificant”. 
But look at a map. Syria has borders with Turkey, Iraq, Israel and Lebanon. Iraq would hardly be buying oil from ISIS and ISIS would hardly be selling it to them. Shia Iraq is in deadly opposition to Salafist ISIS. Lebanon could be a potential customer. But the border areas between Syria and Lebanon are in the main controlled by Syrian government forces.  The “modern, democratic” state of Israel hardly seems a likely candidate. Which leaves… Turkey. Publicly calling for the downfall of the Assad government – and the country with a long-border next to the area of Syria which is controlled by ISIS – the north west. Also the country which Russian satellite images show being the destination for convoys of oil tankers. 
So. The mystery purchaser of all that oil that the West has been admitting to for months does appear to be Turkey. What is “preposterous and kind of ridiculous” is the claim on the one hand that ISIS gains revenue from smuggled oil but on the other to have to keep secret who is buying it.