Originally Posted by TruBlu351
Lean (or less) is for economy cruising or holding.
A rich (more fuel) mixture is for a flight regime where lots of power is required (takeoff, aerobatics etc).
Firstly, thank you to all who answered. I am still studying for my PPL and find the intricate responses most informative, helpful and interesting.
Regarding this above statement by TruBlu351, this means that this "leaning out" can happen at any stage/phase of flight and height?
Thanks,
PE