What is the max memory usage of AC ?

[Gaudin de Beaufort]

I have 8gb of ram.
Does an upgrade to 12gb or 16gb give a better performance of Assetto Corsa ?

 

[Lizard Of Bodom]

I have 8gb of ram.
Does an upgrade to 12gb or 16gb give a better performance of Assetto Corsa ?

yes.
Recently did update from 16 to 32 as was getting over 16GB utilisation on some tracks. When that happens, PC has to use swap file and that is always slower than using RAM directly.
8GB these days is not enough for gaming PC.
If possible try to upgrade to 16 and keep it in Dual Channel( if you have 4 banks and 2x4GB sticks, add 2 more sticks, dont add unpaired sticks as you will loose performance vs dual channel.

 

[Please Stop This]

The size of recorded replay is mostly to blame for huge memory usage, you can adjust here:

Other than that, some crappy tracks with lots of complicated visual walls that also act as physical walls are raising memory usage, also tracks with lots of movable objects are bad for mem usage...