Abstract: Viscometry has been closely associated with the lubricating properties of engine oils since the development of the reciprocating engine. With the advent of non-Newtonian multi-grade engine oils, a new dimension of viscometry was introduced - viscometry at high shear rates and high temperatures. In view of the importance of the critical hydrodynamic lubrication that engine oils provide - and the toll on engine efficiency that these oils extract - it was thought timely and practical to review the initiation and application of high shear rate engine oil viscometry and to discuss subsequent development.