Question 12 DDE04 - Designated Duty Engineer - 1000-4000 HP

The Correct Answer is D **Explanation for Option D (Correct):** In standard engineering practice for internal combustion engines, including diesel generators on marine vessels, the markings on the dipstick (usually marked 'ADD/LOW' and 'FULL/HIGH') define the safe operating range for the oil level. The space between the 'ADD' mark and the 'FULL' mark represents the acceptable range of fluctuation, and operating the engine within this range is safe. If the oil level drops below the 'ADD' mark, the engine is operating with an insufficient volume of oil, which can lead to oil starvation, overheating, and potential catastrophic failure. Therefore, make-up oil is required immediately when the level falls below the 'ADD' (or 'LOW') mark to restore the volume to the safe operating range. **Explanation for Incorrect Options:** * **A) When the oil level drops below the FULL mark on the dipstick.** This is incorrect. It is normal for the oil level to drop slightly below the 'FULL' mark during operation as oil is consumed or settles. Adding oil every time it drops below 'FULL' risks overfilling the crankcase, which is harmful (causing foaming, pressure buildup, and seal damage). * **B) When the oil level drops to between the ADD and FULL marks on the dipstick.** This is incorrect. This range is the *safe operating zone*. While adding oil when the level is near the 'ADD' mark within this zone is good preventative maintenance, adding oil is *required* only when the level drops *out* of this zone (i.e., below the 'ADD' mark). * **C) When the oil level drops to where it is no longer visible on the dipstick.** This is incorrect. While this situation certainly requires immediate attention and oil addition, it represents a critically dangerous and severe lack of oil. Standard procedure dictates that oil must be added much sooner—as soon as the level drops below the designated 'ADD' mark—to prevent the level from reaching this critically low point.