Use of reduced thrust:
On T/O: Reducing T/O thrust, significantly reduces engine wear, keeps greater EGT margins long term- keeps the specific engine operating more efficient.
On climb: CFM/Boeing say fuel savings, climbing at full thrust outweighs long term engine wear.
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CLB = full trust for the climb
CLB1 = an approx 10% derate of thrust (3% N1), (gradually increasing up to full thrust at approx 12000' i think)
CLB2 = an approx 20% derate of thrust (6% N1), (gradually increasing up to full thrust at approx 15000´ i think)
Also the aircraft "should" be preprogrammed so that Climb thrust does not exceed T/O thrust unless selected on CDU N1 page.
So to save the company money, reduce thrust as much as possible for T/O and climb at full thrust once above acceleration height if you are expecting unrestricted climb to above 12-15000'