lubrication, an engine quickly overheats and its
working parts seize due to excessive friction. All
moving parts must be adequately lubricated to assure
maximum wear and long engine life.
PURPOSES OF LUBRICATION
The functions of an engine lubrication system are as
Reduces friction and wear between moving parts
Helps transfer heat and cool engine parts.
Cleans the inside of the engine by removing
contaminants (metal, dirt, plastic, rubber, and
other particles) (fig. 6-19).
Absorbs shocks between moving parts to quiet
engine operation and increase engine life.
The properties of engine oil and the design of
modern engines allow the lubrication system to
accomplish these functions.
Engine oil, also called motor oil, is used to produce
a lubricating film on the moving parts in an engine. The
military specification for this type of oil prescribes that
the oil shall be a petroleum or synthetic petroleum
product or a combination thereof. This oil is intended
for lubrication of internal-combustion engines other
than aircraft engines or for general-purpose lubrication.
Oil Viscosity and Measurements
Oil viscosity, also called oil weight, is the thickness
or fluidity (flow ability) of the oil. A high viscosity oil is
very thick and resists flow. A low viscosity oil is very
thin and flows easily.
Figure 6-18.How oil lubricates.