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.