BusinessGreen: Oil is oil, right? The fuel that powers the cars, jets, tractors and industry that drives the global economy is a commodity. Quality standards ensure, for the most part, that each barrel of oil, each visit to the petrol pump, is the same as any other. Meanwhile, the combination of OPEC and global exchanges set a price, meaning the underlying cost of each barrel of oil is the same. But anyone who peeks beneath the bonnet of the global oil industry quickly discovers that, when it comes to how oil...