In this talk the contribution of molecular simulations and in particular non-equilibrium molecular dynamics (NEMD) modelling techniques providing unique insights into the nanoscale behaviour of lubricants is discussed. NEMD has progressed from a tool to corroborate theories of the liquid state to an instrument that can directly evaluate important fluid properties, and is now moving towards a potential design tool in tribology. The key methodological advances which have allowed this evolution will be highlighted. This will be followed by a summary of bulk and confined NEMD simulations of liquid lubricants and lubricant additives, as they have progressed from simple atomic fluids to ever more complex, realistic molecules. Confined NEMD simulations have revolutionised our fundamental understanding of the behaviour of very thin lubricant films between solid surfaces. This includes the density and viscosity inhomogeneities in confined films, as well as important tribological phenomena such as stick-slip and boundary slip. It is also being increasingly employed to study shear localisation behaviour in thicker films subjected to high pressures.The inclusion of chemical reactivity for additives and their adsorption to metal surfaces and oxides will be also discussed with examples given of how Density Functional Theory (DFT) calculations can be used to provide further insight when the focus is on the physics and chemistry that governs film formation. Coupling between molecular and continuum simulation methods for large systems will also be briefly discussed.