Abstract: The friction and wear of two kinds of fluorosilicone oils as lubricant additives were evaluated on an Optimol SRV reciprocating friction and wear tester by using AISI 52100 steel disc against AISI 52100 steel ball at applied loads of 50 and 200 N, a sliding speed of 0.20 m/s. The wear scar sizes of AISI 52100 steel discs and AISI 52100 steel balls were measured using an optical microscope. The morphologies of the worn surfaces of the AISI 52100 steel discs were examined using a scanning electron microscope (SEM). In addition, the elemental compositions and chemical states of several typical elements on the worn surfaces of the steel discs were examined by means of X-ray photoelectron spectroscopy (XPS). Results indicated that the evaluated tribo-pair under lubrication of PAO base oil using fluorosilicone containing oils as lubricant additives exhibited higher wear-resistance and lower stable friction coefficients than that in pure PAO base oil. This is partly attributed to tribophysical and tribochemical reaction between the lubricant and the sliding surfaces.