The biodegradability of petrol based engine oils produced by African Petroleum (AP) filling station was investigated for a period of twenty-eight (28) days. Two different samples of AP engine oils, Visco 2000-SAE20 (V20) and Super-V SAE 20 (S20)) were investigated. Soil from a mechanic workshop in Alakahia village near the University of Port Harcourt, Rivers State, Nigeria served as seed for the biodegradation. The study was carried out at room temperature (27-29 0 C). The pH of the test systems ranged from 6.5 to 7.4. The counts on the first day were2.62x10 5 and 2.47 x10 5 for V20 and S20 respectively.Whereas the corresponding counts in 28 th day were 2.70 x10 6 and 1.86 x10 6 in colony forming unit per milliliters (cfu/ml). The hydrocarbon utilizing bacteria (HUB) isolated include Bacillus, Citrobacter, Micrococcus, Proteus, Pseudomonas, and Vibrio. The physicochemical analysis showed that nitrate, phosphate, sulphate, biochemical oxygen demand, (BOD), oil and grease content and total organic carbon (TOC) decreased with time. The rate of biodegradation between the two engine oils was in accordance with the normal growth rate for a close system.

Biodegradability of visco 2000-SAE20 (V20) and