This paper reports the optimization of base oils composition involving oleate-based bio-lubricant that results in minimal wear scar diameter (WSD) and coefficient of friction (COF) using Mixture Technique (MT) with Simplex-Lattice Design (SLD). The lubricants used were Neopenthylglycol Dioleate (NPGDO), Trimethylolpropane Trioleate (TMPTO) and Pentaerythritol Tetraoleate (PETO), which all are products of transesterification process between oleic acid and different types of alcohols becoming oleate ester. Fourball tester (FBT) was employed to evaluate the resulting COF under ASTM D4172 B testing procedure while WSD was measured under an optical wear-scar measuring device. A second order polynomial mathematical model was built and able to statistically predict the resulting WSD and COF of lubricant mixtures. In pure form, PETO exhibited the lowest COF with 0.06555 followed by NPGDO (+5.25%) and TMPTO (+16.97%). Meanwhile, NPGDO recorded the smallest WSD with 0.451mm, followed by PETO (+4.04%) and TMPTO (+8.89%). Under SLD optimization technique, pure PETO was shown to give out the lowest COF, however, the lowest WSD was recorded by a mixture of 80.661 wt.% PETO with 11.603 wt.% TMPTO and 7.736 wt.% NPGDO resulting in 0.444mm WSD; 5.53% lower wear than pure NPGDO.