The rate of biodegradation of diesel engine oil by microorganisms isolated from garage soil (petroleum contaminated soil)
was studied. Modified diesel engine oil medium was used and two most abundant microorganisms were isolated from
garage soil – Micrococcus sp. and Pseudomonas sp. were found to be hydrocarbon degraders and these two bacteria’s
were selected for the degradation test. The degradation of diesel engine oil was monitored at a five day interval up to
twenty five day period, using gravimetric method. After 25 days of incubation period, Pseudomonas sp. degraded 67.57 %
of the oil and Micrococcus sp. with 52.95 %. But the mixture of Micrococcus sp. and Pseudomonas sp. were found to have
great potential to degrade diesel engine oil i.e. 89.98 % after 25 days. The rate of degradation of diesel engine oil by
Micrococcus sp. was found to be 7.48 x 10-4gm/hr and that of Pseudomonas sp. was 9.55 x 10-4gm/hr while the mixture of
both bacterial isolates showed highest rate of degradation of diesel engine oil i.e. 1.27 x 10-3gm/hr.