purchased ord-yyz for dec.
base fare K was S$145 (~US$106). business fare P was S$445 (~US$327)
after ticket, was offered upgrade for S$134 (~US$100) and booked into Z.
after reading this wiki - i was wondering whether to rebook/cancel etc. then realised that for accrual to my SQ Krisflyer program - K and Z both accrue at the same rate.