Grease is a semi-solid, high viscosity lubricant made of lubricating oil, thickening material (soap or fatty acid) and different additives to improve viscosity, durability or resistence. Grease is either used as a sealant, or to lubricate parts that can't be lubricated frequently, or, to reduce friction between two parts where oil would not stay in position. Wear metal detection and particle quantifier index are the two tests usually prescribed for grease.
