Question 51 OSE01 - Chief Engineer - OSV

The Correct Answer is C ### Why Option C is Correct Option C states: "Replace the oil more frequently when the engine is exposed to dusty conditions (such as arc welding in the engine room), and replace the oil more frequently when the oil is unusually dirty or when it thickens." Oil bath air cleaners trap contaminants (like dust, dirt, soot, or metallic particles) in the oil reservoir. The effectiveness of the air cleaner depends on the oil being able to capture and hold these particles. 1. **Exposure to Dusty Conditions:** If the operating environment becomes significantly dirtier or dustier (e.g., due to welding fumes, sand, or other construction/maintenance activities), the oil will become saturated with contaminants much faster than normal. To maintain proper engine protection, the oil and the cleaner unit must be serviced (oil replaced) more frequently than the standard schedule. 2. **Oil Condition:** The purpose of changing the oil is to remove trapped dirt. If the oil is visually "unusually dirty" or if it has "thickened," it indicates that the oil is heavily contaminated or has started to break down. Thickening can also be caused by excessive trapped dirt. When the oil is heavily contaminated or too thick, its ability to properly circulate within the air cleaner and effectively capture new particles is severely reduced. Therefore, deviation from the standard schedule should mean replacing the oil *more frequently* to restore the cleaning efficiency. In summary, any condition that increases the contamination rate or reduces the oil's effectiveness necessitates a reduction in the service interval (i.e., replacing the oil *more frequently*). ### Why Other Options Are Incorrect **A) Replace the oil less frequently when the engine is exposed to dusty conditions...** This is incorrect. Dusty conditions overload the air cleaner quickly. Replacing the oil *less* frequently would allow the cleaner to become ineffective, potentially leading to engine damage from ingested dirt. **B) Replace the oil less frequently when the engine is exposed to dusty conditions... and replace the oil less frequently when the oil is unusually dirty or when it thickens.** This is entirely incorrect. Both conditions (dusty environment and dirty/thickened oil) are signals that the cleaner is working hard and its capacity is being exceeded, requiring *more* frequent replacement, not less. **D) Replace the oil more frequently when the engine is exposed to dusty conditions... and replace the oil less frequently when the oil is unusually dirty or when it thickens.** This is partially incorrect. While it correctly identifies that dusty conditions require more frequent replacement, it incorrectly suggests that dirty/thickened oil (which is a clear sign of saturation and reduced efficiency) warrants *less* frequent replacement. Dirty or thickened oil means the air cleaner is failing, necessitating immediate or more frequent servicing.