In this work, we present experimental data on the behavior of model additives adsorbed at the solid/liquid interface as a function of pressure. We report that some additives adsorbed from non-aqueous solvents exhibit rather little variation with pressure, while others exhibit more significant changes. We also display the important pressure dependence of added water. This pressure dependence is relevant, indeed central to many commercially important situations where the adsorption of molecular species to the solid/liquid interface under high pressure is key, such as wind turbines, and this work should help in understanding how protective, anti-wear, or friction-reducing agents can persist (or not) under these extreme conditions. With a very significant gap in the fundamental understanding of the role of pressure on adsorption from solution phases, this important fundamental study provides a methodology to investigate the pressure dependence of these academically and commercially important systems. In the best case, one may even be able to predict which additives will lead to more adsorption under pressure and avoid those that may desorb.