The aim of this study was to investigate the effect of crankcase oil on the cellular and func-tional integrity of rat skin. Thirty (30) rats were randomly grouped into six viz groups A–F. Group A (base-line control) received 2 ml of distilled water. 2.5 %, 5.0 %, 7.5 %, and 10.0 % v/v of the crankcase oil were prepared using unused oil as solvent and 2 ml of the concentra-tions were topically administered to groups C–F respectively for seven consecutive days. Group B served as positive control and received 2 ml of the unused oil. The rats were sacri-ficed 24 hours after the last administration, and blood and part of the skin were collected. Al-kaline phosphatase (ALP), acid phosphatase (ACP), superoxide dismutase (SOD) and malondialdehyde level in the blood and skin samples collected were evaluated. Elemental analysis of the crankcase oil was also carried out. The result revealed high lead, iron and chromium levels. Blood lead concentration of rats was significantly (P<0.05) high after seven days of administration. ALP level in skin and serum increased significantly (P<0.05) with the concentration of crankcase oil. There was a significant decrease (P<0.05) in skin ACP activity while it increased significantly (P<0.05) in the serum. Similar results were observed in the SOD levels of the serum and the skin. The level increased significantly (P<0.05) in groups D–F when compared with controls. The MDA concentration of both serum and skin were signif-icantly (P<0.05) elevated. This suggests toxic potential of used lubricating oil and its potential predisposition to cance