What does dark oil in a car engine indicate?

Dark oil in a car engine often indicates that it has not been changed recently. As engine oil circulates, it collects dirt, soot, and debris, leading to a darker appearance over time. Fresh oil is usually a lighter color, so as it ages and becomes contaminated with particulates, it darkens. Regular oil changes are crucial for maintaining engine health, as old or contaminated oil can lead to increased wear on engine components. This darker coloration serves as a visual cue for drivers that the oil requires immediate attention, emphasizing the importance of maintaining a regular oil change schedule to ensure optimal engine performance and longevity.