Results of tribological testing of stable colloidal dispersions of detonation nanodiamond (DND) in combination with other lubricant additives in mineral oil, greases as well as in polyalphaolefin (PAO) oil are reported. The synergistic effect of combining DND with polytetrafluoroethylene (PTFE), copper nanoparticles or a commercial additive Vanlube (non-phosphor containing anti-wear additive) is reported. Testing of the formulations using ring-on-ring, shaft/bushing and four ball test techniques was performed. The test results reveal more than 80-90% decrease of friction coefficient, about 50% decrease of a diameter of wear spot as well as several times increase of extreme pressure failure load for certain formulations. A strong synergistic effect when using a combination of DND/PTFE additives was observed by a sharp decrease of friction coefficient. It was also demonstrated that the use of smaller DND aggregate size (10nm versus 120nm) resulted in better lubricating performance of PAO-based oil formulation. (C) 2010 American Vacuum Society. [DOI: 10.1116/1.3478245]