Total smooth surfaces like my phone glued so tightly that tears off almost the covers when I want to remember it.
But:
On the grained surface of the instrument panel is not holding.
Even an empty plastic eyeglasses case with flip roughened surface, placed on the non-slip mat, holds less than 2 minutes.
Other tests in the moving car I've saved me.
One can therefore not rely on a flat rate that keeps the anti-slip mat anywhere.