Oilers/Plant Tenders (HHC) Civil Service Practice Exam

Which property is essential for lubricating oil to perform under high temperatures?

1. Low viscosity

2. High thermal stability

3. Acidity

4. Low volatility

The correct answer is: High thermal stability

High thermal stability is essential for lubricating oil to perform effectively under high temperatures. When oils are exposed to elevated temperatures, they can undergo chemical changes that may lead to degradation, loss of viscosity, and the formation of harmful deposits or sludge. Thermal stability ensures that the oil can maintain its properties and performance characteristics, such as effective lubrication and protection of engine parts, even when subjected to continuous heat and stress. Oils with high thermal stability will resist oxidation and breakdown, thereby prolonging their service life and maintaining engine efficiency. In high-temperature environments, oils that lack thermal stability can result in increased friction, wear, and potential engine or machinery damage, making this property crucial for reliable and safe operation. In contrast, low viscosity is not beneficial at high temperatures, as it can lead to inadequate lubrication. Acidity can indicate the breakdown of oil and the presence of harmful compounds, which are undesirable. Low volatility is important for minimizing evaporation loss but does not directly relate to the oil's ability to perform under high temperatures as thermal stability does.