Quote from a C152 POH & AFM and a C172N POH:
To achieve the recommended lean mixture fuel consumption figures shown in Section 5, the
mixture should be leaned until engine RPM peaks and drops 25-50 RPM.
Could you let me know on which section you found that, Iāll have a look at mine. Thanks!
C152, Section 4, amplified procedures.
C172, Section 4, normal procedures.
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Indeed I found it! Very interesting, had never noticed it. Thank you.
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Iām super late to this topic, but, Mike Bush is one opinion in this argument. There are others.
And again, this is just another set of opinions.
Personally, I tend to lean ROP because thatās what I was taught was better for the engine cylinders in the carburated planes I flew, and safer in case you forgot to enrich appropriately again before you land. In the 152ās and Cherokees I flew, above 3-4000ā I could see/hear a change in rpm as I changed the mixture. Slight, but it was noticeable. And if youāre flying out of a 5000ā airport, youāre definitely going to be leaning the mixture to get enough power to take off in a reasonable distance on a hot summer day.
I personally have no clue if the sim is modeling the behavior properly or not. It does seem like I have to pull the mixture quite a bit to lean it properly as I climb, more than Iād expect. But, then again, Iām flying mostly the 152 and have only flown the Bonanza and C172 G1000 a couple of times and that was at between 3-6000ā ftā¦ If you guys feel like itās broken, I aināt got no dog in that fight 
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I notice while on the ground the mixture does absolutely nothing. You can lean out the Baron to almost cutoff and the rpm wont budge at all as you work the mixture levers through 90% of their range.
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Yes, the mixture in the Baron appears to be inoperative, except at cutoff. It has no effect on engine RPM, EGT, or CHT. In other planes, such as the Bonanza G36, the mixture adjustment affects the RPM, EGT, and CHT, but full rich mixture causes a drop in fuel flow (which is very rare in real-life operations at sea-level).
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Hi,
Well I donāt see any contradiction between what Mike is presenting in his book, compared to those opinions. What āshockedā me was the idea of air cooling the engine. As far as I know, air is not able to cool the engine at allā¦ what ācoolsā the engine as we go lean of peak, is that power is going downā¦ I will say, however, that those opinions are from non-mechanicsā¦ so I take them with a grain of salt. My opinion is - if youāre leaning at all, itās already better than many pilots I know
Personally, in real life, Iām just careful that Iām way below 75% power. Preferably below 70%, and then, regardless of where I am with the mixture, I canāt do any damage. Typically, I lean until I detect engine roughness, and just twist it back in enough that the roughness is gone, and Iām good. I donāt even really care about EGT because I know Iām running as clean as possible, also as efficiently and safe as possible (as a clean engine is a safe engine).
Hereās another interesting opinion (but mostly facts) - Shell Aviation Report Lacks Modern Data
Certainly a discussion that is very interesting for me! If you have more resources, Iād love to read them.
Cheers,
Bruno
Yeah, it was just the first link I came upon in which people were fighting over it, haha
I didnāt mean to imply either are right
Orā¦ that I know what Iām doing 
I just know that as long as Iāve been reading about how to fly (and flying), Iāve watched people fight over it
(For instance, Iām thinking back to Lindberghās studies during WWII about increasing the range planes could fly through proper engine managementā¦ Not that Iām that old )
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So it looks like this issue is gonna be fixed on update 6! Awesome, canāt wait!
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For real?? I missed the Q&A!
Watched it and youāre right update 6 ahh!! So glad to hear this. They hadnāt previously given any indication that they had seen this thread lol
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if update 6 means the v 1.10.7.0 , then I see not difference in the mixture behaviorā¦
1.10.7.0 is update 5
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okayā¦ thanksā¦ then still hope 
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Iāve been testing this out too, hopefully Iāll have some changes coming up in a MSFS_C152 update
Official Forum Post keep an eye out here!
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Mixture still does not work. The mixture lever only works as fuelcutter. On or off.
In the FS history the mixture lever functioned since the beginning of FS1.
This lack doesnāt bring MSFS foreward to the hall of fames!
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Wait for update 6, which supposedly will fix it.
Thatās only the case in the Baron.
On all other aircraft mixture works in the same wrong way as in e.g. FSX and P3D.