What are optimal fan settings for my MacBook/iMac/..?
The short answer is: experiment! First observe how temperature sensors behave under automatic fan control. Then try using some custom fan settings. Learn more about temperature sensors here.
Why is Macs Fan Control reporting 0rpm for one of my fans?
It's ok if you have MacBook Pro 13 inch 2015/2016, these models turn off the fan when the CPU temperature is low enough. If you have another model, it most likely means that the fan did not report any data to MFC. It is possible that one of your fan's is dead (there's physical damage to the fan or its cable). Please check your computer with the Apple Hardware Test (it's on the DVD that comes with your computer) and see if it reports a failure with one of your fans.
The app asks for a password. Which password is that?
Macs Fan Control asks for the macOS administrator password when you decide to change fan control. It must be done only initially and when you install the update (when a new version of the app is released). Please don't ask us what YOUR computer's password is.
Does Macs Fan Control work in virtual machines (VirtualBox, Vmware, Parallels)?
No, MFC doesn't work in virtual machines and will never be able to do that. It's not technically possible.
Why isn't the app on the Mac App Store?
MFC uses low level access to mac hardware information. Though this method is publicly available (IOKit interface), this is not allowed on the Mac App Store.
How do I uninstall the app?
On macOS simply quit the app and drag it from the application folder to the trash. On Windows you need to run its uninstall program. Uninstall Tool can be helpful here.
Why do I have high CPU usage by kernel_task when using Macs Fan Control?
Thermal issues are causing kernel task to preemptively use up CPU to prevent overheating. Try putting fan(s) back to auto and if it doesn't help, try to reset the SMC.