Diesel-contaminated soil exhibits altered engineering properties that can affect the stability of overlying structures. Standard consolidation tests were conducted on artificially contaminated soils with varying oil contents. Results show that increasing diesel content leads to higher compression coefficients and lower consolidation coefficients. The results demonstrate that diesel-contaminated soil exhibits increased susceptibility to deformation and requires extended consolidation time. Microstructural analysis reveals that diesel contamination causes pore blockage, particle agglomeration, and oil film encapsulation. Based on experimental data, we propose a modified Terzaghi one-dimensional consolidation theory, developing a consolidation model that considers oil-water synergistic effects and saturation evolution. Model validation demonstrates improved accuracy in long-term settlement predictions under high contamination and high-stress conditions, indicating strong engineering applicability. This research provides theoretical support for diesel-contaminated soil remediation and foundation design in polluted sites.