For nearly 50 years, most of the world’s oil has been bought and sold with US dollars. But that may be changing, as the energy exchange center in Shanghai has begun trading a yuan-denominated oil futures contract. Six months after the contract, more 10% of the world’s oil is now traded in yuan. Why are the Shanghai contracts so popular? Will the world enter a petrol-yuan era from petrol-dollar era? How will the situation evolve against the background of trade war between the two largest economies?