Demulsifier – An additive that promotes oil/water separation in lubricants that are exposed to water or steam.
Density – Mass per unit volume of a material.
Detergent – An important component of engine oils and some industrial lubricants such as paper machine oils and hydraulic fluids; helps control deposits by preventing contaminants of combustion from directly contacting metal surfaces and, in some cases, by neutralizing acids. A detergent is usually a metallic (commonly barium, calcium or magnesium) compound such as a sulfonate, phosphonate, thiophosphonate, phenate, or salicylate. Because of its metallic composition, a detergent leaves a slight ash when the oil is burned. A detergent is normally used in conjunction with a dispersant.
Dewaxing – Removal of paraffin wax from lubricating oils to improve low temperature properties, especially to lower the cloud point and pour point.
Dispersant – An additive that helps prevent deposits by holding the insoluable products of oil oxidation and fuel combustion in suspension in the oil.
Dropping Point – The temperature at which grease passes from a semi-solid to a liquid state, as specified under ASTM D556.