PROPERTIES OF LUBRICANT

 The Lubricant used in I.C Engines should have some properties for the successful performance of the engine. The properties required for a good lubricant are listed below :

 i) Viscosity :

     Viscosity is defined as the measure of fluid resistance to flow. Viscosity of the lubricant decreases as temperature increases and vice versa. This property is very important property of  lubricant because it determines how efficiently oil film separates the moving surfaces from each other and prevents them rubbing. If high viscosity ( i.e , Too Thick ) oil is used, it will lead to power loss, higher operating temperature and excessive wear. If low viscosity oil is used , it cannot lubricate properly and leads to rapid wear of  moving parts.

ii) Oiliness :

     It is the property of an oil to spread and attach itself firmly to the bearing surfaces. In general, high oiliness is required for better lubrication.

iii) Fire Point :

    The Fire point is the lowest temperature at which the fuel burns continuously. Fire point should be higher than the flash point.

iv) Volatility :

    When the lubricating oil is exposed to a high temperature for long time, it may evaporate . This property is known as volatility. The lubricating oil should have low volatility. 

v) Flash Point :

    Flash point of the lubricant is the temperature at which it forms vapors and produces combustible mixture with air. The high flash point is always desirable because low flash point leads to burning of lubricant. The minimum flash point of lubricating oil used in I.C Engine Varies from 200 to 250*C.

vi) Pour Point :

   It is defined as the temperature below which oil will cease to flow in the pipeline under controlled test conditions lubricants having lesser pour point are always recommended as its flow will start even when the engine is started in cold weather.

vii) Delergency :

  The lubricating oil should carry away small particles worn out carbon particles to keep the interior of the engine clean known as delergency.

viii) Neutralisation :

   The lubricating oil should be neither acidic nor alkaline otherwise it will have corrosive action on the parts of the engine. 

ix) Foaming :

   It is the condition in which minute air bubbles are held in the oil. It will reduce the mass flow and also accurate oxidation. Therefore, the oil should force from foaming trouble. 

x) Emulsification :

  The lubricating oil should not form an emulsion when brought in contact with water. A good lubricating oil must not emulsify easily.