Getty Images Aliko Dangote made his money through sugar and cement Petrol production at Nigerian business tycoon Aliko Dangote’s $20bn (£15.5bn) state-of-the-art oil refinery ought to be some of the best business news Nigeria has had in years. But many Nigerians will judge its success on two key questions - firstly: "Will I get cheaper petrol?" Sorry, but probably no - unless the international price of crude drops. And secondly: "Will I still have to spend hours watching my hair turn grey in a hypertension-inducing fuel queue?" Hopefully those days are gone but it might partly depend on the behaviour of what Mr Dangote calls "the oil mafia". For much of the time since oil was first discovered in Nigeria in 1956, the downstream sector, which includes the stage when crude is refined into petrol and other products, has been a cesspit of shady deals with successive governments heavily involved. It has always been impossible to follow the money, but you know th...