Originally Posted by
futuramadramallama
Not OP, but is it correct that an "immediate-upgrade" via cash or Avios (if either are available) will convert the fare class or somehow otherwise result in earning more Avios and tier credits? Whereas a bid upgrade (which is only possible via cash) will earn per the original fare class?
Only the "immediate-upgrade" via cash should earn you extra tier credits and avios. Using Avios to upgrade will still only net you the original economy fare tier credits and avios similar to the bid system in this case.