A process for upgrading hydrocarbon oil feedstreams employs a solid adsorption material to lower sulfur and nitrogen content by contacting the hydrocarbon oil, with a solid adsorbents in a mixing vessel; passing the slurry to a membrane separation zone to separate the solid adsorption material with the adsorbed sulfur and nitrogen compounds from the treated oil; recovering the upgraded hydrocarbon product having a significantly reduced nitrogen and sulfur content as the membrane permeate; mixing the solid adsorbent material with aromatic solvent to remove and stabilize the sulfur and nitrogen compounds; transferring the solvent mixture to a fractionation tower to recover the solvent, which can be recycled for use in the process; and recovering the hydrocarbons that are rich in sulfur and nitrogen for processing in a relatively small high-pressure hydrotreating unit or transferring them to a fuel oil pool for blending.