The lubricating effectiveness of solid-lubricant dispersions are investigated in both point and line contacts using surfaces with both random and directional roughness characteristics. Friction and wear data obtained at relatively low speeds and at room temperature indicate that the existence of solid lubricants such as graphite, MoS2, and PTFE in a plain mineral oil generally will not improve the effectiveness of the oil as a lubricant for such surfaces. Under boundary lubrication conditions, the friction force, as a function of time, initially depends upon the directional roughness properties of the contacting surfaces irrespective of whether the base oil or dispersions are used as lubricants.Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Lubrication Conference in Hartford, Connecticut, October 18–20, 1983