Lean Mixture

[Redroach]

I want to discuss about this one.
I've flown fighters almost exclusively so far, and, based on my crude, limited experience, I won't cry out "Bug!", but I think some chat about mixture would surely be warranted.

So, has anyone found some plane/alt/throttle setting where lean mixture is actually flyable (that is, with the engine running smoothly and probably fuel-saving)? I've yet to encounter such a situation. Surely, Messerschmitt's mixture is set automatically, so something could go on there behind the curtain, but I've definately not been able to use lean mixture successfully with RAF fighters.
And, as stated, I'm not into bombers yet.

Has someone made better/different experiences? Or should it even be that way?

P.S.: General rants a la "the whole FM is corrupted" are of little help here only