Lubrication System in an Auto mobile

A running engine develops a great amount of internal friction and heat between its parts.Lubricating oil has the capacity to absorb and reduce friction and dissipate the resulting heat. To supply lubricating oil between the moving parts of an engine e.g.  gap between piston rings and cylinder liner/bush, is termed as lubrication. Mobil oil which is viscus in nature, is mixed with petrol in the ratio 1:20 which means that in one litre of petrol, 20 ml will be the mobil oil.

Functions of Lubrication Oil: In an automotive engine, there are five important functions of lubricating oil:

• To minimize friction and wear.
• To cool the engine by carrying away  heat.
• To seal the piston and hence preventing escape of gases in the cylinders with least loss of power.
• To cushion the various parts of the engine against vibrations and impact as lubricating oil is viscous in nature and it absorbs vibrations and shock/impact loads.
• To clean the various parts of the engine when the piston during its movement from one position to another .

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Main Properties of Lubricants:

1. Viscosity: Viscosity is a measure of the resistance to flow or the internal frictionof an oil i.e. concentration. As we all know that frictional force or friction is due to interlocking of atoms, similar to interlocking tiles. Common example to understand viscosity is we have two droplets: one water and second honey/mobil oil. The viscosity is measured by Viscometer.
2. Flash Point: The flash point has been defined as the lowest temperature at which the lubricating oil will flash when a small flame is passed across its surface. When the lubricating oil is heated, it reaches a temperature at which a small flame is brought near it, a flash spreads across the oil.
3. Fire Point: If the lubricating oil is heated further after the flash point has been reached, the lowest temperature at which the lubericating oil will burn continuously, is called as fire point.
4. Pour Point: The lowest temperature at which oil can be poured is termed as pour point. It is this property which enables the oil to flow through oil galleries. This property must be     considered because of its effect on starting an engine in cold weather.
5. Specific Gravity: The mass of oil  per unit volume is termed as density, while specific gravity is a measure of the density of a lubricating oil. It is measured with the help of a hydrometer, which floats in the lubricating oil and the gravity is read on the scale of the hydrometer at the surface of the oil.
6. Cleanliness: A lubricating oil must be clean. It should not contain dust or dirt particles. These impurities may either be filtered out or removed with the change of oil at periodic     intervals i.e. during service.
7. Adhesiveness: It is the property of lubricating oil due to which the oil particles stick with the metal surfaces (e.g. at the outside surface of the piston and inside surface of cylinder bush), hence absorbing excess heat generated due to friction as piston reciprocates inside the cylinder.
8. Oiliness: An oil is said to be an oil when it has oiliness. This property is highly desirable in helping the lubricant to adhere/stick to the cylinder walls.

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