AbstractOlefin copolymers and terpolymers (OCPs) are used as viscosity modifiers in a large proportion of the European and world multigrade oil market. The polymer properties of the basic ethylene propylene polymers are critical to the physical characteristics of the final lubricant and its engine performance. The important parameters are discussed. Ethylene propylene polymers intended for use in other industrial applications should be checked thoroughly to avoid potential field problems. Modifications of these speciality OCPs to dispersant polymers enhance diesel and dispersant lubricant properties, enabling the most severe lubricant performance requirements to be met. The paper also reviews developments reported in the literature on the production and handling of the products together with their application, particularly with reference to their effect on low temperature properties, engine cleanliness, wear and fuel economy of the lubricant.