Right you are, fpuentegomez.
The MCDU last time I flew airbus only allowed for one holistic 'mission' CI to be entered and this will cover CLB, CRZ and DES phases of the trip.
So what we did at briefing stage, was to enter OFP/FPLN CI into the MCDU and brief accordingly from those predicitions, and then after departure and SID complete, whilst still in 250/FL100 regime, change the CI to "0" approaching the high speed climb regime at FL100 or equivalent point. Thereafter, from FL100 until ToC or next most restrictive clearance, we would conduct climb at CI=0 Airbus with managed speed set (Vy) -or- Boeing Vref30+140 (80+60). Finally upon reaching ToC and before ALT*/VNAV PTH becomes the active speed mode, enter again the dynamic cost index that was briefed on the ground, from the OFP/FPLN and conduct the remainder of the cruise and descent speed portions I.A.W. the OFP FPLN CI.
The purpose of this entire thread was to garner opinion, and see if there is more data out there from operators who (do?) use this technique. So far as I know it was used at British Airways and Alitalia. Surely a few others have tried it. Why did they try it? Did it work? Are they still doing it? Why didn't it work?
In my own trials, I have found that savings on a wide body twin can be pushing upwards of 300-400kg at times, and slightly less on a narrow body. But, this does not always hold true (ISA dev, Weight, step climbs {and what to do with that extra vertical energy during a step climb: turn it into forward speed}, differences airframe by airframe and so on.}
I would be delighted to hear from anybody who has tried this on a tri- or four-engined aircraft, or from anyone who has aircraft performance expertise in these aircraft also.