I have used QF upgrade credits to upgrade from D to F on a OWE business class fare. A QF member can use QF points or upgrade credits to upgrade any QF sector operated by QF (must book the QF flight number if available as a codeshare), providing there is availability.

OWE in Y (booked as M class) is considered discount ecconomy, so use the correct column in the tables for number of points or credits requried for upgrade to J.