Question 16 MODE02 - Assistant MODU Engineer

The Correct Answer is C ### Why Option C (neutralize acids) is correct: The **Total Base Number (TBN)** is a measure of the reserve alkalinity in a lubricant, particularly diesel engine lube oil. Diesel engines produce combustion byproducts, notably sulfur oxides (when sulfur is present in the fuel), which form corrosive sulfuric acid (and carbonic acid from combustion). The TBN value indicates the oil's ability, via alkaline additives (detergents), to **neutralize these acids**, thereby preventing corrosive wear on engine components (like bearings and cylinder liners). A higher TBN value means the oil has a greater capacity to neutralize acids over its service life. ### Why the other options are incorrect: **A) resist changes in viscosity with changes in temperature:** This property is primarily measured by the **Viscosity Index (VI)**. Oils with a high VI resist thinning significantly at high temperatures and thickening excessively at low temperatures. TBN does not directly measure this characteristic. **B) resist emulsification:** Emulsification resistance (the ability of the oil to separate quickly from water) is a function of the oil’s formulation and demulsibility characteristics, often tested using specific water separation tests. While TBN-imparting additives (detergents) can influence other properties, TBN itself is not the measure of resistance to emulsification. **D) resist oxidation at high temperatures:** The ability to resist chemical breakdown when exposed to heat and oxygen is measured by **oxidation stability**. This property is primarily managed by **antioxidant additives**. While a strong TBN retention is important for overall oil life, TBN is specifically a measure of acid neutralization capacity, not oxidation resistance.