Class 4 (4th Engineer) MEP 📅 Oct 2025

Exam Question

With respect to the properties of fuel oil, explain the significance of the following terms:

(a) Calculated Carbon Aromaticity Index (CCAI). (4)

(b) The importance of Sodium to Vanadium Ratio. (4)

(d) Pour point (4)

Reference Answer

### (a) Calculated Carbon Aromaticity Index (CCAI)
The Calculated Carbon Aromaticity Index (CCAI) is an empirical value used to estimate the ignition quality of residual marine fuel oils. It is particularly important because traditional indicators like Cetane Number are not applicable to heavy fuels.
* **Concept and Calculation:**
* CCAI is calculated based on two fundamental fuel properties: Density and Kinematic Viscosity. A higher density and lower viscosity for a given fuel generally correspond to a higher aromatic content, which in turn leads to poorer ignition quality.

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