The aggregation behavior of the PIBSI molecules within the oil environment and their adhesion either to the soot surface or to the engine wall were studied with a two-level simulation approach combining classical, atomistic molecular dynamics (LAMMPS) with dissipative particle dynamics (SciDPD). Electronic and thermodynamical properties of the molecular environment where PIBSI dispersants operate could be derived in semi empirical treatments by MNDO and ab initio applications by Turbomole.