Lubricants for Internal Combustion Engines:
In any internal combustion engine, the lubricant oil will be exposed to high temperatures due to the combustion of fuel in the engine cylinders. Lubricant should be selected in such a way that it can observe the heat and adhere to the surface of moving parts with leaving it properties. Therefore, the lubricants should posses’ high viscosity index (low variation of viscosity with temperature) and high thermal stability; it should neither evaporate easily nor decompose at the operating high temperatures if not lubricant deposits on the surface forming carbon clusters. However as the lubricant are well sealed so that they do not come in direct contact with water, a property of lubricant like emulsification need not be considered at all. Consequently, petroleum oils containing additives, which impart high viscosity index and oxidation stability to them, are used as lubricants for internal combustion engine.
Lubricants for movable and high tense gears:
Gears operate at extreme pressures, so they are required to be oiled for better performance; gear teeth are primary contactors and work distributors so lubricant should stick to the gear teeth well. When gears rotate they provide centrifugal force to the lubricant at the edges and so lubricant can be thrown away making them dry to avoid this lubricant should have an excellent property of adhering to the surface even during high revolutions. Consequently thick mineral lubricating oils, containing extreme pressure additives like metallic soaps and chlorine, sulphur or phosphorus compounds are employed.
Lubricants for delicate instruments: Gadget and Instruments like watches, clocks, scientific equipments, sewing machines etc, are not exposed to high temperature or to water or to extreme load etc, so properties relating to these conditions are not considered for such uses. Consequently for such purpose thin vegetable and animal oils line palm oil, neat oil is employed.
Lubricants for very high pressure and low speeds such as for tractor, rollers, concrete mixers, lathes, and railway track joints etc. Under these conditions oil/grease films cannot be maintained. So solid lubricants like graphite, soapstone, mica etc are employed either in dry powder form or as emulsion in oil or water. Lubricants for high pressure and low speeds like rail axle boxes, wire ropers, tractor rollers etc are greased and blended with thick oils.
Lubricant for spindles in textile industry: for spindles moving at very high speeds thin oils are used. For better results, oxidation and rust inhibitors are added to the oil.
Lubricants for refrigeration systems: oil with low pour-points low viscosity and low cloud point is needed. So naphthalene-base oils, possessing such characteristics, are according employed mostly. The pour-point requirements are -400F for the lightest grade and -130F for the heaviest grade oils. Their viscosity range is 85 to 325 Sayblod Universal Seconds at 1000F.