The search for environmentally friendly materials that have the potential to replace mineral oil in various industrial applications is considered a priority research in the lubricant, fuel and energy sectors. Accordingly, vegetable oils seem to be a significant potential base fluid and a substitute for mineral oil as grease formulation. The aim of this paper is to study the comparison of jojoba and castor oils as base fluids for producing lithium lubricating greases. In this respect, the sulfurization of jojoba and castor oils was carried out at temperatures ranging from 110 to 170oC. The physicochemical properties of Sulfurized jojoba and castor oils are found better than non- Sulfurized oils. The flow and viscoelastic properties of these oils have been studied by programmable Rheometer HADV-III ultra system that operates in either a steady rotation or in an oscillatory mode. The obtained data reveal that the flow behavior depends to a large extent on the nature of the aforementioned oils. Jojoba oils exhibit properties close to castor oil except for oxidation stability which is better in case of jojoba oil. The influence of these oils and their Sulfurized products on the properties of the prepared biogreases was studied. The data obtained in this investigation indicate that the prepared biogreases from Sulfurized oils had superior properties with respect to dropping point and consistency compared to non- Sulfurized oils. The prepared greases from jojoba oil and its sulfurized product showed improvement in oxidation stability than corresponding grease based on castor oil or its sulfurized product. An opposite trend was observed concerning the consistency and flow properties. It is concluded that the jojoba and castor oils showed appropriate properties to be used as fluids for bio-lubricating greases. In addition, performance characteristics of the obtained greases are largely dependent on the type of base fluid.