AbstractThis paper reports on some work concerned with the synthesis and characterisation of three lubricating greases based on animal bone fat, cottonseed soapstock, and a mixture of them both. The physico‐chemical properties of these fats were established and showed them to be good thickeners in the preparation of different types of greases. It was shown that the growth of the soap structure and grease consistency depend on the type of fat as well as on the viscosity of the lubricating oil in the grease formulation. The greases so synthesised were assessed in accordance with standard NLGI grades and Egyptian standards. Their rheological and thermal behaviour was studied, which revealed that the synthesised greases have significant yield stress at normal operating temperature and good flow properties. It was concluded that the above mentioned fat by‐products are suitable for producing grea