An Experimental Study to Investigate the Extent to Which Internal Combustion Engine Oils Retain Their Properties

Abstract

Internal combustion engine oils are important fluids found inside car engines and are directly connected to them. These oils play a very important role in the engine service period and extend its life. The purpose of this study is to investigate the extent of change in the properties and specifications of the lubricating oil for a sample of gasoline engines after using them for varying distances. This study came in support of previous studies by increasing the number, age and quality of samples. In this study, several experiments were conducted at the Libyan Oil Institute and Zawiya Refinery on Thuraya oil (SW50-10), which is used in spark ignition engines (gasoline), for samples of engines of different types and distances (100,000 km - 250,000 km) and operating periods (3000 km - 6000 km). In addition to measuring the viscosity property, which is considered one of the most important properties that can be relied upon to measure the life of the used oil, some other properties of no less importance than the viscosity property were studied in this research, these properties are density, pour point, flash point, ash percentage. Samples of used oil from four engines of different types of cars (CITROEN HYUNDAI, IZUZI, and DAEWOO LANOS) were taken. The results of this study showed that the rate of change of the studied properties was clear and noticeable for the samples and different operating periods. The density ratio increased between the distance (3500 km) and (6000 km) from 0.26% to 1.27%, respectively. The rate of change in the viscosity of the oil decreased significantly at different operating periods from 5% to 23%. There was a clear change in the pour point compared to the new oil from -24^oC to -21^oC, as well as the flash point from 225^oC to 180^oC, and it was also observed that the ash ratio increased at different operating periods (3500 km, 4000 km, 6000 km) to 65%, 0.66%, 0.69%, respectively.