It is found that, when solid bodies are in static contact with liquid lubricants containing surfactants and cholesteric liquid-crystal compounds, the behavior of their adsorption depends on the adsorbent nature and chemical composition. When copper, steel and glass powders are in long contact with oleic acid solutions in Vaseline oil, the additive concentration decreases, and in the case of solutions of cholesteric liquid–crystal compounds, their concentration in oil increases. When metals (friction pair steel–steel) are in dynamic contact, adsorption processes involving solutions of liquid crystal compounds occur by other mechanisms. The increase in the adsorption activity of cholesteric liquid-crystal compounds in the friction of solids is established. It is found that changing the concentration of liquid-crystal additives in the used oil due to the adsorption tribo-activity in the process of dynamic contact correlates with a decrease and a subsequent stabilization of the friction coefficient of the steel–steel pair.