Why Does Engine Oil Deteriorate?
2 Answers
Engine oil deterioration occurs due to the following reasons: 1. Water contamination in the oil: Experiments show that when the water content in the oil exceeds 0.1%, the added antioxidants and dispersants in the oil become ineffective, accelerating the oxidation process of the oil. When the water content reaches 1% or more, the lubricating properties of the oil deteriorate, viscosity decreases, leading to premature oil degradation and rusting of components in mild cases, and in severe cases, causing serious mechanical failures such as engine seizure or bearing damage. 2. Cylinder wear or piston ring damage: This allows fuel to enter the crankcase, reducing the oil's viscosity.
I have noticed that oil degradation is primarily the result of chemical and physical changes. When the engine is running, high temperatures expose the oil to environments above 200°C, causing oil molecules to oxidize and break down, forming acidic residues and sludge. Contaminants such as dust, moisture, unburned fuel, or metal particles can further degrade the oil's quality. Additives are designed to clean and protect the system, but they gradually deplete over time, losing their buffering capacity. With prolonged use, the oil thickens and darkens, reducing its lubricating effectiveness. If the oil is not changed regularly, it can accelerate component wear and corrosion. Moisture infiltration is also an issue, especially in humid climates, potentially causing emulsification, which affects the oil's viscosity and flow performance. Maintaining a regular oil change schedule is key to prevention.
