Passenger Car and Heavy Truck Cold Cranking Studies - Effects of Oil Viscosity and Vehicle Type

Abstract

In the 1960's and 1970's, engine cold cranking studies on reference oils served as a basis for the development of a standardized laboratory test which measured an oil's viscosity under the appropriate temperature and shear rate conditions (the Cold Cranking Simulator or CCS). However, when the original CCS method (Apparent Viscosity of Engine Oils at Low Temperature Using the Cold-Cranking Simulator, D 2602) was modified to reflect a change from single temperature determinations (-18°C) to a multi-temperature method, concerns regarding test precision and the response of viscoelastic oils prevented the revision of the method to an ASTM standard. The recent development of modified CCS procedures to address these concerns has been somewhat hindered by the lack of available reference oils with supporting engine cranking data. To address this need, Esso Petroleum Canada initiated a limited study of engine cold cranking on four test oils, in 1987. Five different late model passenger cars equipped with 4- and 6-cylinder gasoline engines were subjected to repeated cold starts at temperatures between -15°C and -25°C in an All-Weather Chassis Dynamometer facility. The vehicle cranking results and samples of the test oils were forwarded to the CCS task force in 1987. More recently, Esso Petroleum Canada has undertaken a detailed cold start/pumpability evaluation of multigrade engine oils in three different heavy duty trucks. Cold cranking data from these diesel engines, in addition to the previous gasoline engine studies are discussed with respect to oil viscosity, operating temperature and vehicle effects.