Biological source oils, including, but not limited to, algae oil, stabilize the presence of asphaltenes in petroleum feedstocks, such as crude oil, to help avoid or prevent problematic issues caused by the asphaltenes, such as sludges, plugging, deposits, fouling and/or corrosion in the production, transferring and processing of the petroleum feedstocks. Chemical additives such as phenol-based resins, and reaction products or combinations of long chain alpha-olefins and/or small chain aldehydes and/or long chain alkyl phenate sulfides and/or metal oxide-based colloidal hydrocarbon-based nanodispersions, may also stabilize the presence of asphaltenes in petroleum feedstocks. By “stabilizing” is meant keeping the asphaltenes in solution in the petroleum feedstocks.