Engine oil or lubricating oil has a major effect on the engine life and the proper operation of any engine. Changing the engine oil before it is due increases a customer’s cost. The lubricating oil in every engine performs many functions such as reducing friction, preventing corrosion, protecting the engine against wear, removing all impurities, lubricating the moving parts, and cooling the engine parts. There are several causes for the deterioration of lubricating oil, including the properties of the oil, oil quality, and high engine temperatures. Consequently, the deteriorated oil must be replaced at a specified mileage or at specific time intervals to get the best engine performance. It is very important to know when to change the oil, because changing the oil too late can affect the engine parts and vehicle performance. However, replacing the oil too early influences the economy and environment and is an inefficient use of depleting resources. This study describes the kinematic viscosity, flash point, and fire point of multigrade Society of Automotive Engineers (SAE) 0W-20 Totachi (Totachi Industrial Co. Ltd., Japan) international brand oil, which has a 10,000 km guarantee and is approved by and used in 10 different vehicle brands, to determine the rate of deterioration of the parameters. These parameters are the most important physical behaviors of lubricating engine oils. Having information about these parameters is very important for maintaining an engine’s lifespan. The results of this study showed that after 10,000 km, the Totachi oil parameters such as the kinematic viscosity at cold start, at 40°C and at 100°C, the flash point, and the fire point decreased by 22.03%, 25.98%, 26.75%, 16.94% and 17.34%, respectively, from the base values, and that the oil is suitable to use for 10,000 km.