This study aimed at developing a laboratory scale packed bed reactor (PBR) and evaluating its performance in re-refining of used lubricating oils. Used and unused motor oil samples of two brands (Mobil Super SAE 20W-50 and Total Quartz 5000 SAE 20W-50) were used in this study. The sorbent materials were a blend of diatomaceous materials in the same mass ratio. The compound types of the oils eluted from the PBR and those of used and virgin oil samples were studied for comparison. FTIR spectroscopy was employed to observe the variations in the types and nature of functional groups present in the various oils as well as to estimate the oxidation products of the oils using peak area increase (PAI). The constituent organic compounds were also identified and quantified using GC-MS. The results revealed that some of the compounds exist in different isomeric forms in the oil samples. The similarity in the classes of compounds is affirmed by their very similar FTIR spectra. GC-MS results indicated that the used oils contained the highest number of compounds, followed by the treated oils and also indicated similar treatment effects on the brands of lubricating oil. The study concluded that the developed reactor is a viable and sustainable technique for re-refining of used lubricating oils.