FWIW...I used Castrol Transmax Z Fully Synthetic ATF during my recent C36 AMG transmission ATF fluid change. I am very impressed with the quicker gear engagement and silky smooth gear changes.

http://www.castrol.com/liveassets/bp_internet/castrol/castrol_australia/STAGING/local_assets/downloads/a/AU_Castrol_Transmax_Z.pdf