(Rick Durden) writes:

It doesn't hurt
to lean it when taxiing as well, but do so very aggressively, so that
if you forget to go to full rich before takeoff it will quit on you
rather than make a takeoff with the mixture other than at full rich.

Rick, I had a talk with my mechanic a couple of months ago about
leaning when idling. He says for my carburator and C-90 engine, and I
suppose many other aircraft engines, leaning at idle doesn't do
anything unless it is nearly at idle cutoff. It is only when the RPMs
are well above idle that the mixture control begins to really control.
So does leaning on the ground--during idle--do anything unless it is
leaned nearly to idle cutoff?