Some reflections are made about the object of a recent debate on the role played by the viscous dissipation term in the local energy balance equation. The debate regards both clear fluids and fluid saturated porous media. A strong accent has been placed on the role played by the pressure work term in the local energy balance. In the present brief contribution, it is suggested that the focus on the pressure work is not the most convincing escape from the possible paradoxes of viscous dissipation. On the other hand, another focus is proposed, namely the most appropriate formulation of the energy balance in the framework of the Oberbeck-Boussinesq approach to the description of buoyant flows. (C) 2008 Elsevier Ltd. All rights reserved.