Diesel contamination in the soil may occur in different ways, and its interaction in the soil is uncertain and may have negative impacts. This paper presents the interaction between clay soil with moisture content of 30% and diesel content of 1%, 3% and 6% of dry mass. The soil is taken from Colombia to know the effect of diesel on the index properties (moisture content, specific gravity of solids, Atterberg limits), cation-exchange capacity, mineralogy composition and unconfined compression strength; moreover, the samples are tested at different temperatures considering if it is known the presence of diesel or not in the soil because the presence of diesel increases organic components, then if there is known the presence the temperature is 50 ± 5 °C but 110 ± 5 °C. The diffractograms showed that diesel did not affect the mineralogical composition in the exposure period of 7 days, but in real cases the hydrocarbon may be for prolonged periods, months or even years. Independent of the test temperature, there was an increase in moisture content and decrease in specific gravity of solids as diesel content increased. The Atterberg limits had an uncertain behavior by the presence of diesel and change in the test temperature. The cation-exchange capacity was increased by the presence of diesel independent of the test temperature. The parameters of unconfined compression strength decreased as diesel content increased. The research concludes that diesel effects over geotechnical parameters of the soil generates negative impact, and projects that have soils with diesel need special attention, so it is important to keep doing research where diesel has more time of exposition in the soil.