Abstract: The effect of five detergents on friction reduction and wear resistance of lubricating oil under water pollution was studied by using high frequency reciprocating rig. The results showed that all detergents tested enhanced the anti-wear and anti-friction properties of the base oil. The detergent C with high base value had the best lubricating effect on base oil, and the friction coefficient was only 0.10. Water had little influence on the anti-wear performance of oil samples with detergent A, B and E, but had greater influence on the anti-wear performance of oil samples with detergent C and D. When the addition of detergent C (w) was 2.0% and the addition of water (w) was 0.1% and 0.3%, the average wear scar diameter of the steel ball increased to 410.0 μm and 416.0 μm, respectively, and the wear resistance of the oil product became significantly worse. For detergents containing the same organic acid matrix type, the stronger the water solubility of overbased components is, the larger the wear scar diameter of steel balls when corresponding oil products are tested; oil products containing the same metal type and different organic acid matrix detergents have different trends in friction coefficient and wear scar morphology.

Key words: water, detergent, anti-wear and friction reduction properties, base value, friction coefficient