At what color should engine oil be changed?

[LaAriel]

Engine oil should be changed when it turns brown and becomes opaque. To check, place a drop of oil on a test paper and observe the spread. If the edges of the spread are not clearly defined, the oil is still usable. If a ring forms, the oil can still be used. However, if the ring is very distinct and the spread is minimal, it indicates that the oil needs to be changed. Engine oil, also known as motor lubricant, serves multiple functions such as lubrication and friction reduction, aiding in cooling, sealing to prevent leaks, rust and corrosion prevention, and shock absorption. Engine oil consists of two main components: base oil and additives. The base oil is the primary constituent of the lubricant, determining its fundamental properties, while additives compensate for and enhance the shortcomings of the base oil, providing additional performance characteristics, making them an essential part of the lubricant.