Cold cranking viscosity of used synthetic oils originating from vehicles operated under similar driving conditions

Abstract

This article assesses the performance and reduction level of five engine oils available from various manufacturers. The trend and intensity of the cranking viscosity changes as measured in the cold cranking simulator were thoroughly analysed. In the presented experiment, alterations in engine oils appearing during actual operation were noted. The tests were conducted under conditions which can be depicted as 'harsh', that is, multiplied starting of the engine, extended engine idling and short stretch driving. All of the engine oil samples were collected from passenger cars of a homogeneous fleet of 25 vehicles. The dynamic (cranking) viscosity was determined according to the ASTM D5293-15. In all analysed cases, there was a dangerously rapid increase (36%-69%) in the cranking viscosity, and the limit values (7000 mPaÁs) were reached very quickly (for the mileages in the range of 3000-13,000 km). The obtained results have led to the development of a statistical model, allowing vehicle users/drivers to choose a better engine oil in winter, thus improving the engine's ability to cold start and protecting it from excessive wear or damage. The test results may help to predict the performance of the engine oil during operation, its service life and an oil-change interval.

Experimental Investigation of the Viscosity Parameters Ranges—Case Study of Engine Oils in the Selected Viscosity Grade

“…In addition to the comparison of the viscosity parameters provided by the manufacturers or resulting from the SAE J300 standard with the values from laboratory tests, it was also decided to explore the KV behavior at the sub-zero and above 100 • C. The kinematic viscosity measured at −20 • C is indirectly related to another very important parameter-structural viscosity (measured in the CCS apparatus-Cold Cranking Simulator), which determines engine starting ability at low temperatures [16,28]. A lower value of such viscosity corresponds to an easier start of the engine at low temperatures and means less load being put on the car battery.…”

“…The result for sample #36 is particularly worrying. The research carried out by the authors previously [16] showed that in −30 • C, too high kinematic viscosities may indicate not meeting the requirements of SAE J300 classification in sub-zero temperature parameters (CCS). As a result, it was decided that CCS measurements should be performed for two extreme samples (#13 and #36).…”

“…From the point of view of optimal lubrication of machines and devices, lubricating oils should slightly change their viscosity as the temperature changes, i.e., the viscosity change curve should have the smallest possible angle of inclination [15]. This facilitates starting at low temperatures, and at high temperatures ensures optimum lubrication through the durability of the oil film [10,16]. The dependence of viscosity changes on temperature is characterized by the viscosity index (VI).…”