Oil infiltration from industrial infrastructure such as conduits, shafts, and subsurface loading chambers represents a significant environmental concern, particularly regarding soil contamination. This study investigates the temporal effects of oil contamination on the geotechnical properties of sand, including shear strength parameters, volumetric behaviour, permeability, and particle arrangement. Laboratory experiments were conducted using sand samples with varying oil content percentages to evaluate these alterations systematically. Results demonstrated an initial decrease in shear strength and permeability immediately following oil contamination. However, long-term monitoring revealed a significant increase in these parameters during ageing. Similar patterns of engine oil content effects were observed in the loose sand configuration, with the magnitude of the impact being notably more pronounced. These findings provide crucial insights into the long-term behaviour of oil-contaminated sandy soils and have important implications for geotechnical engineering practices in areas affected by oil spillage