Mixture in this game is a bit of a mystery for me, has its own logic I suppose, but Asobo didn’t gave any manual 
I would really like the mixture in MSFS to be at least in the same logic as IRL, even if not accurate.
BTW, it’s the same on all props and even on turbines, the way you feed the turbine is also broken.
Oh and prop RPM is also broken (not logical according to real life) on all the prop aircrafts…
Could you expand on your point about prop RPM? I’ve been spending a lot of time flying the Bonanza G36, and the RPM control seems reasonable (though I’ve only ever flown fixed-prop trainers in real-life, so I may not know what to expect). The mixture is definitely incorrect, though. The fuel flow gauge drops quite a bit when advancing the mixture from 90% to 100%. This is completely bonkers. Fuel flow should continue increasing with mixture. It results in totally anemic power output in the Bonanza when operating at full rich mixture, which is standard on takeoff and approach.
While the mixture is indeed way too sensitive to altitude (shouldn’t have to lean under 3000 above sea level-ish), it’s not a given that higher mixture results in higher fuel flow.
If your mixture is so rich that it makes the engine RPM drop, the engine will gulp down less of that richer mixture, resulting in lower fuel flow. Tune it in just right, and the engine RPM will increase, sucking down a lot more of the less rich mixture.
Sim is way overdoing this though.
to put it simple : in MSFS, high AOA of the prop / high RPM is translated to “more speed everytime”, which is absolutely not the case irl. You can cruise quite faster in a lower rpm setting irl.
Feathering is also feeling strange, but I have very few irl experience with that part to quantify what I feel isn’t right…
Increasing mixture does not equal increased fuel flow. It’s all about fuel/air ratio.
Here’s a good primer.
Edit: Misunderstood that you were saying higher mixture doesn’t always mean a higher fuel flow in every circumstance. Ignore me. But whatever the sim does where it has a sharp decrease in fuel flow passing 91% rich at sea level is very much wrong.
Oh, thank you for the explanations, @Seven7Tango and @MortThe2nd. I was aware that engine power can decrease if the mixture is too rich at high altitude, but I didn’t realize that could also translate into a lower fuel flow when the mixture is rich.
Still, as @MortThe2nd mentioned, the behavior of mixture in the sim is inaccurate. The drop in fuel flow should happen at high altitude, but in the sim, fuel flow drops substantially when I increase the mixture from 90%-100% at sea level. To get proper climb performance, I need to lean the mixture before taking off. That is completely ridiculous.
Is this also an issue on the Carenado aircraft?
so, if at sea level, enriching the to full should have no effect on fuel flow and only rpm
if at elevation, then enriching the mixture past the balance point of maximum output (given constant rpm demand on blue lever) should yield a raising of rpm and higher fuel flow and higher egt as a direct result of more efficient fuel burn.
when a “too rich” mixture is ignited in the cylinder, the temperature of the explosion is cooled by the unburned excess fuel and the fuel compresses reducing cylinder pressure, lower power throughput, thus rpm.
so, the fix would be to calculate the ambient air density at the aircraft versus at sea level to derive a percent
then take that percent and apply to the mixture input.
above that setting, fuel flow and rpm are reduced by a particular modifier, separately defined to allow full control of engine tuning.
below that setting, fuel flow and rpm are reduced by a different modifier with a cutoff threshold where rpm is at a minimal amount akin to idle rpm.
below the cutoff threshold, engine dies
i learned a long time ago never complain about an issue unless you define the issue and come up with a roadmap to a resolution…even if the result is incorrect, it can drive those implementing the fix down a new path that leads to the actual resolution.
The mixture control in Flight Sim is broken. Leaning at Sea Level? C’mon! 
Submit this on Zendesk 
To add to that… once you’ve found max rpm (usually around 50%) you can leave it there the entire flight.
On the list of things that need fixing this is way down the list, but it would be nice at some point to make it work at least a little bit correctly…
I’m bummed this thread doesn’t have more votes. Likely because the average simmer never looks at the fuel flow gauge and doesn’t know what the mixture does 
I know, right? I think a lot of people enjoy the “big tubes” simply because so many threads are about them.
I almost always fly GA aircraft. The closest I’ve gotten to a high-flyer is the TBM… that is one seriously nice aircraft!
I get the appeal of flying the tubeliners… it’s something most people can’t do in real life, and you feel powerful controlling a larger machine. But it takes away from the fun of actually flying by hand and navigating a route because the FMS does it all.
That’s exactly it. Most of my real-world time has been in Cessnas and Pipers, with the nod to the high-wing aircraft.
In Flight Sim, the “feel” of the C152 is pretty darned amazing. I swear you could run someone through forty hours of training following a real world flight school plan, and they could jump into a C152 and feel right at home.
It’s pretty amazing!
i usually dont use the fuel pumps except during landing and other maneuvers that require it (per POH), so most of the time, they’re off…leaning the mixture never does anything so for me, they stay at 100% the whole flight 
What I’ve found is do a run up - 2000 rpm with parking brake set - and lean for best rpm. After that it’s “set and forget.”
Agree with the fuel pump… takeoff and landing only.
my first hair-raising experience in MSFS was during alpha when I tried one of the landing challenges…i was high on short final and felt the need to slip it in…so i dipped a wing, kicked in the rudder and it was just freaking unblievable. I also liked how the mixture leaning worked at sedona as it felt very accurate…which is why i’m floored that it is sooooo broken on the premium baron?
I agree it is really fun… and some of the A/C “feel” incredibly real. It is a disappointment that the mixture is either wonky or inop in some models.
They’ll get to it I’m sure… they have a steep mountain to climb with more critical issues right now, and that’s entirely understandable.