Cracks for high sulphur fuel oil (HSFO) extended gains on Friday, while 0.5% low sulphur fuel oil (VLSFO) cracks dropped amid a flurry of selling interest, trade sources said. Singapore 380-cst HSFO cracks closed at discounts of about $2.60 a barrel, maintaining at more than two-year highs. The market received a boost amid a tighter …