Assessment of the possible impact of spent engine oil on the soil ecosystem is imperative for the determination of environmental acceptability. This study investigated this impact ex-situ using standard laboratory tools to determine the following parameters: pH, temperature, moisture content, and total petroleum hydrocarbon (TPH). The experiment demonstrated that at 1.0 – 3.5% contamination over time across days-zero to -28, spent engine oil upset the physicochemical equilibrium of the soil. A significantly reduced (p<0.05) pH in the range of 7.1 ± 0.00 to 6.2 ± 0.00 meant that the soil was acidic with a significant (p<0.05) increase in temperature from 33 ± 0.00 to 35.5 ± 0.03oC at increased concentrations overtime. The moisture content increased significantly (p<0.05) from 3.5 ± 0.00 to 19.31 ± 0.01% following the significant increase (p<0.05) in total petroleum hydrocarbon (TPH) from 0.002 ± 0.00 to 0.084 ± 0.00. This presupposed a hydrocarbon polluted soil ecosystem with oxygen deprivation; a demonstration of disturbed ecological equilibrium.