Question 29 3AE01 - Third Assistant Engineer

The Correct Answer is B **Explanation for Option B (Correct):** Option B states: "When the oil level drops below the ADD mark on the dipstick." The ADD mark (or LOW mark) indicates the minimum safe operating level for the engine oil. If the oil level falls below this mark, there is insufficient oil for proper lubrication, cooling, and pressure maintenance, risking severe engine damage. Therefore, make-up oil is required immediately when the level reaches or falls below the ADD mark. **Explanation of Incorrect Options:** * **A) When the oil level drops to where it is no longer visible on the dipstick.** This level is critically low and far below the minimum safe operating level (ADD mark). Waiting until the oil is completely off the stick means the engine has been operating, or is about to operate, in a dangerously starved condition, which could lead to catastrophic failure. Make-up oil should have been added much earlier. * **C) When the oil level drops to between the ADD and FULL marks on the dipstick.** If the oil is between the ADD and FULL marks, it is within the safe operating range. While adding oil at this point is sometimes done for proactive maintenance, it is not *required* until the level hits the ADD mark. * **D) When the oil level drops below the FULL mark on the dipstick.** The FULL mark indicates the maximum safe level. Since the engine consumes oil during operation, the level will always drop below FULL shortly after running. It is completely normal and safe for the oil level to be slightly below the FULL mark (as long as it remains above the ADD mark). Adding oil every time the level drops below FULL would lead to constant, unnecessary topping off, and potentially overfilling the crankcase.