Singapore’s high-sulphur fuel oil (HSFO) margin flipped from a discount to premium on Friday, extending gains from the previous day after the U.S. imposed more sanctions on Iran. Singapore’s March 380-cst HSFO/Brent crack (FO380BRTCKMc1) closed at a premium of 53 cents a barrel on Friday, holding onto more than five-year highs, LSEG data showed. The …