Modified Reciprocating Viscometer Predicts High Temperature Cranking Properties of Engine Oils

A reciprocating viscometer which was used for determining cold-cranking properties of engine oils was modified so it could be used to predict low-speed, hot-cranking properties of crankcase oils in full-scale engines. Since the current 210 F ASTM D 445 viscosities of multigrade oils fail to predict their hot-cranking properties, there is need for such a unit. A high degree of correlation was obtained between the 210 F viscosities determined with the modified reciprocating viscometer and those determined using a full-scale test engine for a group of V.I. improved oils and a group of commercial premium multigrade crankcase oils. The correlation obtained between the two units for a group of 5W oils containing oiliness agents indicates the viscometer to be satisfactory for screening tests. In general, this viscometer can satisfactorily predict low-speed, hot-cranking properties of oils in full-scale engines quickly and economically.