THE EFFECT OF VISCOSITY INDEX IMPROVERS ON VISCOSITY OF ENGINE OILS

The effect of viscosity index improvers on viscosity of engine oils was investigated. Under a certain amount of viscosity index improver, the model describing the changes of final oil viscosity with the viscosity of base oil is a liner equation with an intercept. This result does not agree with the equations developed by Kraemer or Huggins, which have been widely used now for describing the changes of the oil viscosity with the added viscosity index improvers. After the test results were analyzed, a new model ν=ν 0+ w(c 1 ν 0+c 2w ) was generated as described in this paper. There are some physical meanings in this equation. c 1 represents the influence of the viscosity of base oil on the thickening power of the viscosity index improver. c 2 represents the influence of the rate of the viscosity index improver in the oil on the thickening power of the viscosity index improver. The analysis results show that the model developed is more precise than the Kraemer or Huggins equations.