Levels of heavy metals in used lubricating oils from automobiles

Oil is used to lubricate vehicle components such as engine, transmission systems, hydraulic system, differentials and drive ends to prevent metal wear and tear on such moving pa1ts. Oil also inhibits corrosion, improves sealing and cools the moving parts of the automobile. Wear and tear, however, is common to lubricated vehicle parts when oil loses its lub1ication suitability due to various reasons including viscosity degradation. This study was aimed at assessing levels of heavy metals in used oils from automobiles parts as a result of metal wear and tear. Used oil samples were collected from various vehicle components (engines, transmission systems, hydraulic systems, differentials and final drives) at Bulyanhulu gold mine maintenance workshops. The oil samples were analyzed for iron (Fe), zinc (Zn), and copper (Cu), chromium (Cr), lead (Pb), cadmium (Cd), manganese (Mn), nickel (Ni) and tin (Sn) levels by a Rotating Disc Electrode Atomic Emission Spectrophotometer (RDEAES). Levels of the corresponding metals in new oils were used as control. The results showed that the levels of heavy metals in used oils were significantly different from their counterparts in new oils except for zinc in engine and hydraulic oils, manganese in transmission and hydraulic oils and tin in engine oils. The concentration (ppm) ranges for these metals in used oils were as follows: Fe (45.3 - 1681.1), Zn (64.97- 1260.6), Cu (14.8 - 785.4), Cr (0.5 -19.9), Pb (1.4 - 107.1), Cd (0.5 - 1.0), Mn (0.0 - 45.0), Ni (0.2 - 45.6) and Sn (0.0 - 82.3). Surprisingly, toxic metals such as lead, chromium and cadmium were found in used oils at high concentrations. For instance high levels of lead were observed in transmission and differential oils whereas chromium was high in oils from final drives. High levels of cadmium were found in used oils from both differentials and final drives. Since used oils from automobiles were observed to have significantly high levels of heavy metals, it is recommended that spillage, discarding and disposal of waste oils should be controlled so as to save the environment from this contamination. Heavy metal recovery plans such as the recycling and use of such waste oils as energy sources in steel and cement industries should be institutionalized and practiced nationally.