  Previously, the Einstein equation has been described as an equation of state,
general relativity as the equilibrium state of gravity, and $f({\cal R})$
gravity as a non-equilibrium one. We apply Eckart's first order thermodynamics
to the effective dissipative fluid describing scalar-tensor gravity.
Surprisingly, we obtain simple expressions for the effective heat flux,
"temperature of gravity", shear and bulk viscosity, and entropy density, plus a
generalized Fourier law in a consistent Eckart thermodynamical picture.
Well-defined notions of temperature and approach to equilibrium, missing in the
current thermodynamics of spacetime scenarios, naturally emerge.
