—Applying nonequilibrium statistical mechanics we focus on nonequilibrium corrections Δs to entropy and energy of the fluid in terms of the nonequilibrium density distribution function, f. We also evaluate coefficients of wave model of heat such as: relaxation time, propagation speed and thermal inertia. With these data a quadratic Lagrangian and a variational principle of Hamilton’s type follows for a fluid with heat flux in the field representation of fluid motion. We discuss canonical conservation laws and show the satisfaction of the second law under the constraint of these conservation laws.