Assessment of the level of contamination from possible impact of spent crankcase oil on soil ecosystem is imperative for the determination of environmental acceptability. This study investigated this impact ex-situ using a culture-dependent approach to evaluate the total microbial counts; biochemical and physicochemical tools to determine the activities of their exudates (acid and alkaline phosphatases), total petroleum hydrocarbon (TPH) and pH as indices. The experiment demonstrated that at 1.5 – 3.5% contamination across days-zero to -28, spent crankcase oil stimulated significantly (p<0.05) the activity of alkaline phosphatase in a concentration and time dependent manner from 4.0 ± 0.03 to 8.0 ± 0.00Katal. Acid phosphatase suffered inhibition significantly (p<0.05) from 6.0 ± 0.05 to 2.8 ± 0.01Katal. The contamination significantly (p<0.05) increased the total petroleum hydrocarbon (TPH) across all the days relative to control and this lowered the pH from 5.9 ± 0.00 to 4.8 ± 0.00. An initial reduction in microbial biomass from 1.32 x 109 ± 0.00 to 3.48 x108 ± 0.00 cfu/g on week one, and induction of hydrocarbon-degrading organisms, (the hydrocarbonclastics), to 3.7 x 10¬¬8 ± 0.10cfu/g at 1.5 – 3.5% contamination overtime correlated with enzyme induction, and activity. Ecosystem dynamics and mineralization were impaired and disrupted and the entire soil biochemistry was altered.