Max or Ave Value for Mesh Stats?
 

I had never thought much about this before, but for most of the mesh stats I don't see a max or min quality being clarified. I've been using average, but if Element Volume Ratio is supposed to be <20 should that be average?

If your question is - what quality do I need to make my mesh for it to work? The answer is that it depends on the simulation. Simple flows (eg low Re single phase) can handle poor mesh qualities. Some flows (eg hi Re flows) require better quality, and some physics models (surface tension is the most stringent I know) require extremely high quality.

For instance in some of my modelling I have shown errors rapidly increasing when the aspect ratio is over about 1.5 using a multiphase surface tension model. But this mesh would work fine without a surface tension model.

So the reason no general figures are discussed is because there is no general rule. It depends on what you are modelling.