Engine Oil

All engines require some form of lubrication and this is provided by the engine oil. This oil is required to carry out numerous different tasks when the engine is in operation, the primary function is to lubricate all the components by reducing friction and preventing or reducing metal to metal contact. The oil stops two  surfaces from touching each other by forming a thin lubricating layer on mating surfaces.

Engine oil mobile oil lubrication lubricants smooth engine running
Engine oil

Functions of engine oil.

The functions of engine oil are as follows-
1.To lubricate the mating surfaces.
2. To cool the engine components and hence help in maintaining their optimum temperature.
3.To clean the different components of engine.
4.To act as a seal on mating surfaces of piston rings and the cylinder block and hence prevent the combustion gases from leaking to the crankcase.

Grades of engine oil

Society of Automotive Engineers (SAE) has developed numerical coding system to grade the engine oils according to their viscosity. SAE viscosity index includes the following numbers: 0, 5, 10, 15, 20, 25, 30, 40, 50 and 60. Lower the number means lower viscosity and a higher number means a higher viscosity.

Monograde engine oil

These oils are not able to maintain optimum viscosity if their temperature changes. They work well only when their temperature is steady. Mono-grade oils become thin as they get heated and become thick as they cool down. Also, a mono-grade oil does not use any additive or viscosity modifier.

Multi grade engine oil

These oils are suitable for use over a wide temperature range. Their viscosity do not change abruptly due to temperature change and remain in an optimum range. They are neither very viscous at room temperature nor very thin at higher temperature.

Why do we need multi grade oils?

The engine oil has to encounter different temperature conditions as the engine operates. When an oil is heated up, its viscosity decreases. The oil must be able to be pumped through the system as fast as possible when it is cold on start-up in order to lubricate all components within a few seconds of the engine starting.  The same oil must then be able to supply sufficient lubrication to all components at higher operating temperatures. Different environments will place different demands on the lubricating oil but it must remain ‘thin’ (low viscosity) enough at the time of cold so that it can flow and ‘thick’ (high viscosity) enough when hot to keep moving parts separated. These characteristics of multi grade engine oil allow it to supply sufficient viscosity at all normal operating temperatures Multi grade oils contain additives that allow them to perform exactly in this manner - not too thick on start-up and not too thin at operating temperature.


Naming of engine oil

Engine oil smooth engine running Mobil oil lubricants lubrication
5W30 oil

The name of engine oil contain some alphabets and some digits. You might notice names as 10W-40 or 5W-50 etc. Here 'W' means that the oil can be used in winter also. Or either it is all weather oil. First digit represent the lowest temperature at which it can flow i.e. 10w30 can flow at 10 degede Celsius and 5we40 starts flowing at 5 degree Celsius. The second digit represents viscosity at 100 degree Celsius i.e .10w40 is more viscous than 10w30 at 100 degree Celsius.  
These were some basic information regarding engine oil. Looking at the importance of engine oil we must always use the quality oil specified by the automobile companies. Always use the recommended grade of engine oil so as to improve the performance of your vehicle.

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