Lean Mixture

[Viper2000]

Originally Posted by IvanK

RAF fighters (and Blenheim) mixtures are Auto Lean and Auto Rich. No other adjustment required. Once selected you should be running in either an automatic altitude compensated LEAN or RICH mixture that's all there is to it.

FTFY

At present (latest patch, tested just now), switching to lean mixture at high altitude makes the engine run rough to the point that the prop governor on a Spitfire IIa won't hold rpm properly. It doesn't break the engine, but it's clearly unhappy.

OTOH, at least I was able to climb to FL200 "full switch" without breaking anything, so that's progress.