Lubricants are used to reduce friction, wear and heat between contacting surfaces in relative motion (Bart et al., 2013a). They can be classified based on physical appearance, i.e. solid, liquid or semi-solid. Liquid lubricants can be derived from petroleum, vegetable, animal or synthetic oils. Grease is a semi-solid material in which the liquid fraction is suspended in a solid matrix of thickener and additives. A solid lubricant is a solid material with a film comprising inorganic or organic compounds such as graphite, molybdenum disulphide and cadmium disulphide (Mobarak et al., 2014).