My understanding is Green Dot is minimum fuel flow per hour and Cost Index 0 is maximum miles per pound / kilogram of fuel.
Therefore, if there will be no delays, CI 0. If you can predict any delays, the sooner you slow to Green Dot the better... unless you do it so soon that you end up flying unnecessary additional time.
Last edited by Ultra Glide; 5th Aug 2013 at 06:46.
Reason: Added "of fuel" to first sentence.