A system and process are provided for recovering and/or cleaning residual or waste petroleum products such as sludge accumulated within a storage tank or upon process equipment surfaces, or from inorganic materials such as sand or clay, and the like. The system and process include a negatively charged aqueous-based dispersion fluid, which is contacted with the petroleum product under controlled relatively high pressure and high shear conditions for fluidizing hydrocarbon molecules and for preventing such molecules from adherence to process equipment surfaces, or contaminants such as sand or clay. Additional mechanical separation as by subjecting the mixed petroleum product and dispersion fluid slurry to sonic vibration may also be employed. The thus-fluidized slurry of petroleum products, dispersion fluid, and inorganic materials can be separated by conventional techniques, as by settling and/or flotation, for further individual processing and/or re-use.