The objective of this study is to investigate the effects of blending a bio-lubricant, specifically pentaerythritol ester, with a motor oil that is widely available in the market. The focus is on analyzing the changes in frictional properties when operating under conditions of boundary lubrication. The objective of this study was to optimize the synthesis of pentaerythritol ester (PE ester) with the aim of attaining a complete conversion to long-chain tetraesters. Furthermore, significant emphasis was placed on the meticulous formulation of the bio-lubricant to mitigate the risk of any potential deterioration in its physicochemical properties upon its incorporation with conventional oil. The research entailed the combination of commercially available motor oil with pentaerythritol (PE) ester obtained from Calophyllum inophyllum. The blending was conducted using proportions of 10 and 20%. The primary idea of this study was to investigate the anti-wear and anti-friction characteristics of the test oils utilizing a pin-on-disc tribometer under boundary lubrication conditions. The bio-lubricant—motor oil blends have demonstrated a substantial decrease in both friction coefficient and wear, particularly when the blending percentage reaches 20%.