Candidates faired well in part (a) of the question. Part (b) and (c) were problematic to the candidates. The required responses to these parts are given below:
(b) The properties of lubrication oil are:
- Body: This is the ability of oil to maintain an unbroken film of oil between the
surfaces in contact;
- Flow: This is the ability of an oil to spread easily over a surface;
- Viscosity: The measure of the rate of flow of oil i.e. thin oil has low viscosity while thick oil has high viscosity.
- Viscosity index: The number given to an oil to indicate the degree of change of its thickness (viscosity) as the temperature changes.
- Oiliness: The ability of an oil to cling to surfaces of be attracted to a metal surface.
(c) Advantages of air-cooled engine over the water-cooled type are:
- It eliminates leakages;
- It is lighter in weight;
- It warms up quickly;
- It operates at higher temperature;
- It is cheaper to manufacture;
- It requires less maintenance;
- It has no risk of damage due to freezing.