free carbon. Which of the following is not a characteristic property of good lubricant? (a) high (b) high thermal stability (c) high oiliness (d) high viscosity index

The question appears to be: **Which of the following is *not* a characteristic property of a good lubricant?** (a) High volatility (b) High thermal stability (c) High oiliness (d) High viscosity index **Correct Answer: (a) High volatility** ### Explanation: **Good Lubricant Properties:** 1. **High Thermal Stability:** Ensures the lubricant can withstand high temperatures without breaking down. 2. **High Oiliness:** Provides effective lubrication by forming a consistent lubricating film. 3. **High Viscosity Index:** Indicates that the lubricant maintains its viscosity over a wide temperature range. **Why "High Volatility" is Not a Good Property:** - **High Volatility** means the lubricant can easily evaporate at lower temperatures. This leads to: - **Reduced Lubrication Effectiveness:** As the lubricant evaporates, it cannot provide consistent lubrication. - **Increased Wear and Tear:** Insufficient lubrication can cause increased friction, leading to faster wear of mechanical parts. - **Potential for Deposits:** Evaporated lubricant can leave residues that may contaminate other components. Therefore, **low volatility** is a desirable property for lubricants to ensure longevity and effective performance. ### Summary: Among the options provided, **high volatility** (**option a**) is **not** a characteristic of a good lubricant. Instead, low volatility is preferred to maintain consistent lubrication and protect mechanical components. **Answer:** (a) high