ok first thing. make sure the engine is warmed up and the oil is at normal cruising temperature. it is pointless leaning a cold engine.
From C182T Manual. "After start set 1000rpm and lean to 1200rpm. Reset 1000rpm with throttle." The difference on the fuel flow is 2gph at 1000rpm.
Even with carburettor engines I was taught to lean on the ground in high temperatures.
Edited to add: My local commercial training school taught their students flying Warriors on cross countries to set full throttle above 5000ft and lean to reqired power setting. The engines nearly always made recommended TBO.
D.O.