This paper deals with the prediction of free heave in expansive soils from central Poland. Thirty-nine soil samples differing in plasticity were selected for a comparative analysis. The soil types examined – Neogene clays, alluvial soils, and glacial tills – differ in CLOD index (C_w) values, which range from 0.027 to 0.019, with values for undisturbed samples being higher than those for the remoulded ones. The variability of the C_w index correlates best with the sand-to-clay ratio. Studies of soils contaminated with diesel oil (ON) have revealed that the C_w index decreases with growing ON content. Calculations of the potential heave, assuming a 1% moisture change for a 1 m thick soil layer, show the heave to be 18 to 12 mm and 15 to 11 mm for Neogene clays and glacial tills, respectively, depending on the in situ void ratio. Petroleum contamination significantly reduces the potential heave of the soil. The present analysis clearly suggests that glacial tills are more susceptible to oil-derived contamination than Neogene clays.