Effect of Newtonian and non-Newtonian oils on minimum ol film thickness in engine journal bearing were investigated at various oil viscosities. The influence of oil viscosity and engine operating conditions on minimum oil film thickness of main bearing and con-rod bearing was examined. Minimum oil film thickness for Newtonian oils increased uniformly with kinematic viscosity. But the correlation between kinematic viscosity and minimum oil film thickness was very poor for non-Newtonian oils. According to the straight-line regression analysis for non-Newtonian oils, high temperature high shear viscosity at 1 $1{ imes}10^6Sec^{-1}$, $150^{circ}C$ increase the coefficient of determination from 0.41 to 0.77. Con-rod bearing showed better correlation between minimum oil film thickness and engine operating conditions than main bearing.