Crude is quoted in dollars, but SNSUC's books finally settle in RMB. At USD/CNY 6.7042, FX commands a sizeable slice of every barrel's landed cost. When neighbouring currencies like the yen or won swing, North-East Asian buyers' landed competitiveness moves with them.

USD/JPY at 156.74 and USD/KRW at 1,353.8 shape Japanese and Korean refiners' procurement cost and export competitiveness. A weaker local currency makes their imported crude dearer but also makes their products cheaper in third markets. For a resale operator, that is the counterparty's FX book and it has to be priced in.

EUR/USD at 1.1339 pulls on European demand and the mismatch in dollar-settled trades. FX is not an appendage of crude; on its own it can erase or amplify a parcel's margin. Coding FX swings into the final step of the quoting model beats discovering post-trade that currency ate the profit.