In what condition should the lubricating oil be replaced immediately?

The replacement of lubricating oil should occur immediately if it becomes emulsified. When oil emulsifies, it means that water has mixed with the oil, typically resulting in a cloudy or milky appearance. This is problematic because the presence of water can significantly reduce the oil's lubricating properties, leading to increased wear on engine components, potential corrosion, and overall poor performance.

Emulsified oil is unable to effectively lubricate and protect engine parts, making it essential to replace it quickly to avoid engine damage. The quick action in resolving this issue helps maintain the integrity of the machinery and ensures a longer operational life.

In contrast, while thickened or viscous oil can indicate a problem, it may still provide some level of lubrication and may not necessitate immediate replacement. Clear oil typically indicates that it's still in good condition and doesn't require urgent action.