This research studied a method of predicting the kinematic viscosities of lubricating base oil blends by measuring the kinematic viscosity according to the corresponding ASTM methods of three types of lubricating base oil and their blends which were prepared by weight method and volume method in various compositions. The parameters were calculated. The results indicated that the calculated parameters vary linearly with the blend composition. These equations gave satisfactory results, which agreed well with the experimental results. With the proposed method, weight method, percentage deviations from the experimental values were significantly smaller than those using volume method. At the temperature of 25 ํC and 100 ํC, absolute average deviations was 4%, but 16% at 40 ํC.