High Speed Climb
It is common knowledge that modern fan-jet engine is at its most fuel efficient self when operating at high altitute.
By performing a high speed climb out (i.e. eliminating the 250 KIAS below 10,000ft ATC restriction), the aircraft would have to spend more time at lower altitute accelerating as compared to above 10,000ft.
How is it then possible to "save" fuel when a high speed climb out is performed ?