The ultradispersed diamond (UDD) powders synthesized by the detonation of explosives with negative oxygen balance are new nano-materials with practical value. In this paper, the detonation soot and UDD powders were used as an additive in paraffin oil. This kind of two-phase lubricant possesses excellent load-carrying capacity, antiwear and friction reduction properties. Under boundary lubricating condition, the detonation soot and UDD powders can easily penetrate into the rubbing surfaces owing to their nanoscale to reduce the wear and friction. The detonation soot is less effective than UDD powders. In addition to sliding, it is hypothesized that a nanoscale ball bearing effect is occurring in the UDD powders which reduces the wear and friction. Presented as a Society of Tribologists and Lubrication Engineers paper at the ASME/STLE Tribology Conference in San Francisco, California, October 13–17, 1996