Abstract: Lubrication is one of the main features influencing both energy consumption and reliability of lubricated mechanisms. Recently ionic liquids became an attractive lubricating material, used as net lubricant or as additives. Protic ionic liquids have a potential in the field of lubrication because they consist of organic acids already having adsorption ability. In the present study we synthesized three ammonium based ionic liquids having different cations and the same anion. As cations t-octylamine, diethanolamine, dodecylamine were used, while oleic acid was employed as anion. During the synthesis corresponding ammonium salts were obtained. Physicochemical and tribological properties of the synthesized ionic liquids were investigated using them as additives in synthetic base oil. It was found that they have different appearance, viscosity and miscibility in the base oils. Despite difference in structure they possess similar tribological properties.