Friction modifiers (FMs) are added to lubricating oils to reduce friction. For severe sliding, reaction film FMs (RF FMs) reduce friction, while adsorption film ashless FMs (AF FMs) do not reduce it. However, for mild sliding, AF FMs reduce friction,while RF FMs do not reduce it. From these perspectives, many studies have been conducted concerning the combined system to cover a wide lubrication range. According to past studies, it was shown that the RF of MoDTC (MoS₂) promotes absorption of ashless FMs. Therefore, if the adsorption force of an ashless FM on the metal surface and the reaction film could be measured,it would help to improve the tribological properties of the lubricating oil. In this study, the adsorption forces on mica, platinum,and copper are measured in non-polar hydrocarbon solvent using colloid probes that are chemically modified with either COOH or CH₃. Consequently, the adsorption forces on mica and copper as measured with the COOH probe are larger than those measured with the CH₃ probe. These results suggest that adsorption forces can be measured with colloid probes, and they show the possibility of distinguishing between chemical and physical adsorption.