The cash premium for very low sulphur fuel oil (VLSFO) in Asia softened for a fourth straight session on Wednesday, underpinned by weaker spot offers and ample supply expectations into June. The premium for 0.5% VLSFO (MFO05-SIN-DIF) slid to $7.75 a tonne to Singapore quotes, though front-month margin (LFO05SGDUBCMc1) rose to a premium of $9.93 …