Soil contamination by various oil products is a serious geo –environmental issue that adversely hampers the quality of soil, underground water and atmosphere. In this paper a comprehensive laboratory-testing program was carried out to compare the engineering properties of an uncontaminated and oil contaminated clay. The comparison between uncontaminated and oil-contaminated clay showed that the contaminated clay behaves as a cohesionless material, due to the formation of agglomerates. The contamination also affects the plasticity and the Cation Exchange Capacity (CEC) of the investigated clay. The swelling pressure of the clay after contamination suffered three times reduction, while no change was observed in the percent swelling of the contaminated clay, and finally the angle of internal friction based on the total stress condition decreases due to presence of oil within the pores. Since crude oil contamination affects the soil physical and chemical properties, therefore developing an effective restoration program in the infected land is necessary
