Abstract: Mini-traction machine is an effective tool to evaluate the frictional behavior of lubricants and additives in elastohydrodynamic lubrication (EHL), mixed lubrication (ML) and boundary lubrication (BL) with appropriate testing conditions. The device also has an excellent ability to differentiate various lubricants and additives. Frictional behaviors of several additives were studied by MTM tester. Test results show that anti-wear property of ZDDP can be much affected by diverse anti-wear additives in fully formulated engine oil. Crystalline sulfonate is sufficiently helpful to reduce the coefficient of traction under BL condition, while it doesn’t show any improvement on the coefficient of traction in EHL and ML lubrications. The frictional properties and effective range of various friction modifiers also have much difference and need to be carefully balanced in practical use.

Key words: MTM, frictional behaviour, engine oil, anti-wear additives, crystalline sulfonate, friction modifier