Most experts agree that the trade in oil products is a component in IS's financing - but no more than that.
It is without doubt an important component earning the group around £440 million a year, according to US authorities and independent experts.
But it is also true that it's not just IS that depends on this oil. In fact it would not be going too far to say that this oil trade overseen by IS is the one resource that is keeping civil society going.
It powers people's generators, especially with the harsh Syrian winter setting in, it provides the fuel for refugees to leave the battlefield, it keeps clinics going.
So central is it to the functioning of the state, that even the Assad regime buys oil from IS's controlled refineries in order to keep the lights on - even in some opposition held areas.
This is the fundamental reason why the US led coalition openly said it had avoided bombing these IS controlled installations. Until now.
The reason? Airstrikes now form the bedrock of the coalition's IS-focused Syria policy.
It has lots of airpower but an ever diminishing list of targets that avoids civilian casualties.
These big open oil facilities represent a ready-made target and they are not set in a civilian area.
Yes hitting them will affect IS finances - but only momentarily
The terror group has many other revenue streams; kidnapping, extortion, enforced taxes in the territory it controls, the sale of looted antiquity and so on. All those will still be around after the oil installations are bombed.
The irony is the only thing that will stop these other revenue streams are...you guessed it, taking IS territory which can only be achieved by...yes, you guessed it again, credible, cohesive ground troops.