Class 4 (4th Engineer) MEKM 📅 Jan 2025

Exam Question

Compare the desirable qualities of the lubricating oil selected for each of the following duties: (16)

(a) Auxiliary diesel engines

(b) Stern tube bearings

(d) Gear case of purifier

Give reason for the differing properties of the oils recommended for these four purposes

Reference Answer

A lubricating oil's properties must be precisely matched to its specific application's operating conditions, including temperature, pressure, potential contaminants, and the nature of the moving parts. The differing properties for the four mentioned duties highlight this principle.
### (a) Auxiliary Diesel Engines
**Desirable Qualities:**
* **High Alkalinity (High TBN - Total Base Number):** The oil must possess a sufficient reserve of alkalinity to neutralize the corrosive acidic products formed during the combustion of sulfur-containing fuels (sulfuric acid).

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