Increased rise of industries and car usage in Nigeria and urban development is exponentially on the increase giving rise to multiple waste generation. Evaluation of the different recycling processes showed that acid-clay process has the highest environmental risk as well as the lowest cost; hence, this work added a treatment method for the slurry produced after treatment with acid-clay method, thereby reducing the environmental concern caused by acid and acid sludge formed in the process. The acid ratio was varied between 0 and 20% and adsorbent ratio between 15 and 25%. Automotive-used lubricating oil and industrial-used lubricating oil were treated using two different samples, acid and adsorbent. An increase in acid concentration showed a significant difference over the properties of oil such as density, viscosity, flash point, and other physiochemical properties nevertheless increasing the amount of acid over the optimum point made on significant change. Varying of adsorbent ratio showed little significant effect to density and flash point, while yield and viscosity were unaffected. Optimum point being at 10% acid and 25% adsorbent gave optimal result. All metal contaminants are substantially removed; total base number was improved, while increase in flash point suggested the method effectiveness. Treatment of used industrial oil was found to be easier to re-refine due to less contamination.