Auto Mechanics Paper 2,Nov/Dec 2014.  
Questions:   1 2 3 4 5   Main
General Comments
Question 5

5.         (a)        State two functions of a carburetor.
            (b)        Explain three properties of engine lubricating oil.
            (c)        State one advantage of an air-cooled system over the water-cooled type.


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.
Powered by Sidmach Technologies(Nigeria) Limited .
Copyright © 2015 The West African Examinations Council. All rights reserved.