When tested by the four-ball extreme-pressure procedure, oil solutions oft-octyl chloride at the 2 percent chlorine level rated approximately equal to oil solutions of di-t-octyl disulfide at the 2 percent sulfur level, and both of these additive blends rated better thann-octyl chloride in oil at the 2 percent chlorine level or di-n-octyl disulfide in oil at the 2 percent sulfur level.n-Octyl chloride and di-n-octyl disulfide in oil at corresponding concentrations of active element were approximately equivalent in additive action.t-Octyl chloride was almost as good at the 1 percent as at the 2 percent chlorine level. Mixtures of di-t-octyl disulfide andt-octyl chloride in oil at the level 1 percent S-1 percent Cl rated approximately twice as well as di-t-octyl disulfide (2 percent S) ort-octyl chloride (2 percent Cl). Some finer points of the action of these additives were investigated by studying time-connected behavior at 50-kg and 100-kg loads. The action of the additives cannot be explained on the basis of their chemical structures only; interactions with the rubbing process in the four-ball machine also must be considered.Presented as an American Society of Lubrication Engineers paper at the ASME/ASLE International Lubrication Conference held in New York City, October 9–12, 1972