Abstract: The friction reducing performance of three oil-soluble inorganic nano-particles including silica (Si), diamond (C) and copper (Cu), used as lube additives was studied. The effect of additive dosage on the variation of PB value, PD value and worn surface diameter, as well as the changing of friction coefficient with time under point contact mood and line contact mood were investigated. The worn surfaces were analyzed by SEM and EDX techniques. Results showed that the friction reducing performance of these three types of nano-particles was varied: under point contact mood Cu exhibited the best friction reducing performance; under line contact mood all of them behaved well, yet C possessed the best friction reducing performance.

Key words: additive, friction reducing, point contact, line contact