Abstract: A process is provided for preparing refined oil comprising removal of nickel by incorporating an effective amount of an aqueous substance in crude oil and forming a dispersion containing water nickel and oil, and thereafter filtering the dispersion containing water, nickel and oil. As aqueous substance, for example liquid water, steam or dilute acid can be used. Small quantities of aqueous substance, usually less than about 4% calculated on the weight of the oil are sufficient. The process can be applied suitably, in particular in relation to hydrogenation of oil. The aqueous substance can suitably be incorporated in the oil before, during or after the hydrogenation reaction but before the filtration of the oil/catalyst slurry, or it can be incorporated after the slurry filtration, in the filtered hydrogenated oil.