Carbon nano-onions (CNOs) have been synthesized by the catalytic decomposition of methane at atmospheric pressure. The catalyst was prepared by a reduction-substitution method. The produced CNOs have a regular shape with concentric carbon layers with an external diameter of about 50 nm. A systematic study of their stability in Group I and III base oils, with and without low amounts of dispersant/surfactants, was performed, revealing the effectiveness of the synergistic combination of SDBS and Tween 80. Tribological tests showed a significant reduction of friction coefficient and wear scar diameter up to 23 % and 20 %.