The objective of this study was the evaluation of the production of base oils for lubricants of biological origin using vegetable and used frying oils as feedstock. The production method was based on a two-stage transesterification process. Initially, fatty acid methyl esters were obtained via methanolysis (first stage), and they were used as feedstock for bio-lubricants production by a second-stage transesterification process with the proper long-chain polyols. The produced oleochemical esters were evaluated based on their flow properties and their oxidation stability, as well as their capability of being renewable substitutes for conventional base oils, such as SN-150 and SN-500 mineral oils. The evaluation showed the remarkable physicochemical properties of these bio-lubricants, such as the viscosity, the viscosity index, and the pour, cloud and flash points, which, in combination with their high biodegradability and non-corrosive behavior, make these bio-lubricants ideal for use in special applications of non-recoverable lubrication or of high risk but low heat load and oxidative potential. This is because the oxidation stability of these bio-lubricants is not comparable to that shown by the used mineral oils and therefore they cannot totally substitute for these mineral oils. The reduced oxidation stability can be overcome by blending the bio-lubricants with mineral base oils at proper blending ratios.