In asphalt manufacture, viscosity is of primary importance to product quality control. It is the one test which, more than any other, is necessary to establish the limits of consistency and workability for both manufacture and end uses. At the present time, 12 grades of cutback asphalts are specified by the American Society for Testing Materials. Viscosity specifications are based on Saybolt Furol values, but because of the nature of the test method and the number of grades of asphalt, viscosities must be obtained at four different temperatures. In an effort to simplify viscosity testting, three Phillips Petroleum Co. refineries started using a kinematic capillary viscometer as a control instrument in conjunction with automatic asphalt blend plants. Two and one-half years' experience have demonstrated its practical ability to measure asphalt viscosity in fundamental kinematic units. Use of Saybolt Furol equipment has been discontinued. Equivalent Saybolt Furol values are now obtained by conversion.