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+ Purpose of lubricants
Keep moving parts apart
Lubricants are typically used to separate moving parts in a system. This has the benefit of reducing friction and surface fatigue, together with reduced heat generation, operating noise and vibrations. Lubricants achieve this by several ways. The most common is by forming a physical barrier i.e., a thin layer of lubricant separates the moving parts.
Reduce friction
Typically the lubricant-to-surface friction is much less than surface-to-surface friction in a system without any lubrication. Thus use of a lubricant reduces the overall system friction. Reduced friction has the benefit of reducing heat generation and reduced formation of wear particles as well as improved efficiency.
Protect against wear
Lubricants prevent wear by keeping the moving parts apart. Lubricants may also contain anti-wear or extreme pressure additives to boost their performance against wear and fatigue.
Prevent corrosion
Good quality lubricants are typically formulated with additives that form chemical bonds with surfaces, or exclude moisture, to prevent corrosion and rust....
Seal for gases
Lubricants will occupy the clearance between moving parts through the capillary force, thus sealing the clearance. This effect can be used to seal pistons and shafts
Transmit power
Lubricants known as hydraulic fluid are used as the working fluid in hydrostatic power transmission. Hydraulic fluids comprise a large portion of all lubricants produced in the world. The automatic transmission's torque converter is another important application for power transmission with lubricants.
[item title="+ What is multi grade oil ?"]
These are oils designed to give better viscosities at both high and low temperatures. Multi-Grade oils are made by adding viscosity index improver. The viscosity of all oils falls as they get hot - and multi-grade oils are formulated to minimize this effect. Multi-grade oils are defined by a viscosity rating at a low temperature, as well as one at 100 C.
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+ What is multi grade oil ?
These are oils designed to give better viscosities at both high and low temperatures. Multi-Grade oils are made by adding viscosity index improver. The viscosity of all oils falls as they get hot - and multi-grade oils are formulated to minimize this effect. Multi-grade oils are defined by a viscosity rating at a low temperature, as well as one at 100 C.
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+ What is an SAE grade ?
SAE Stands for the Society of Automotive Engineers, based in the U.S.A.The SAE grade specifies the most important parameters for engine oil mainly its viscosity. The SAE viscosity classification defines mainly viscosity limits at high and low temperature for any grade of lubricants. The SAE grade guide us to the right viscosity for different outside temperatures. Grades marked ‘w’ stand for winter are at a temperature below 00C.
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+ What does API specification stands for?
API stands for the American Petroleum Institute. This body has specified the performance standards that oils used in road vehicles should meet. For oils to use in passenger car engines, the letters API are followed by a set of two letters such as SM, etc. Service Levels for passenger car oils or ‘S’ indicates for Spark Ignition Engine. These specified performance levels have evolved through the years, from API SA to SN,
Similarly, the API designates the performance of diesel engine oils with a letter sequence such as API CF-4.’C’ indicates for commercial or compression ignition engine. Automotive gear oils they use API GL-4.API GL-5 e.t.c
The highest API for commercial engine oils (diesel oils) today is API CJ-4. -
+ What is viscosity?
Viscosity is a measure of a fluid's resistance to flow. The viscosity of a lubricant decreases as temperature increases and the viscosity of a lubricant increases as temperature decreases .The viscosity of a lubricant is closely related to its ability to reduce friction. Generally, the thinnest lubricant is ideal which still forces the two moving surfaces apart. If the lubricant is too thick, it will require a lot of energy to move the surfaces. If it is too thin, the surfaces will rub and friction will increase.
Viscosity is also useful for identification of grades of oil and for following the performance of oils in service. An increase in the oil's viscosity during use usually indicates that the oil has deteriorated to some extent; a decrease normally indicates dilution with fuel.
kinematic viscosity is a measure of a fluid’s resistance under gravity to flow.SI unit is m2/s while C.G.S unit is cm2/s or stoke
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+ How to select the right viscosity of engine oil?
The viscosity of the engine oil for any application depends on the speed, load, ambient temperatures and the clearance between moving parts. Engine Oil must protects over a wide range of temperatures from cold starts to severe condition. When engine oil perform at both extremes then it is known as “multi-grade” oil that includes SAE ,a number/letter followed by W and a number, such as SAE 20W-40. In a hot climate or driving through a region where a combination of high heat and high-altitude are encountered, the manufacturer will probably suggest for a multi-grade or “all-season” oil such as SAE 15W-40. Such oil has the cold flow characteristics of 15-weight at start-up, yet the coating and protecting property of 40-weight oil at the high temperatures. In a predominantly cold climate, the recommended oil might be a SAE 5W-30. However it is advisable to be guided as given in the operation & maintenance manual provided by the manufacturer.
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+ Why some oils are called a synthetic and others a mineral?
This refers to the origin of the base fluid. Mineral oils are derived by refining processes, essentially a complex series of purification and separation steps, from crude petroleum oil extracted from the ground. Synthetic base fluids are made by chemical processes, generally by building up larger molecules from smaller ones. Because these chemical reactions and starting materials are well defined, the synthetic fluids are not only relatively pure chemicals but are deliberately made to deliver the performance characteristics required in a lubricant
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+ Why are additives used in lubricating oil?
Additives are substances formulated for improvement of the anti-friction, chemical and physical properties of base oils which results in enhancing the lubricant performance and extending the equipment life. Additives provides the anti oxidant,anti wear,anti rust,anti foaming ,detergency and dispersant .e.t.c .property to the lubricant.
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+ What are these additives?
The list below covers most of the additives used. You can see that lubricant formulation is a real science as there are many components and variables, all of which must be balanced out to make a well-rounded product, which is then proven by a series of rigorous tests.
ADDITIVE
WHAT IT DOES
HOW IT WORKS
Oxidation Inhibitor
Prevents varnish and sludge formation on bearings or in circulating systems. Retards aging of the oil. Lengthens service and storage life of oil. Protects oil itself directly (indirect protects metal parts - varnish and acids)
Reacts more readily with oxygen (from air) than does the oil itself, thereby retarding oxidation of the oil. Inhibits the formation of free radicals, an important chemical species in the oxidation process, thus slowing oxidation reactions
Rust Inhibitor
Prevents rusting of ferrous (iron or steel) machine parts
Forms a film on ferrous metallic parts thus protecting them from attack by water and air, or other destructive material.
Corrosion Inhibitor
Prevents corrosive attack on non-ferrous metallic surfaces
Forms a film on non-ferrous metallic parts thus protecting these parts from attack by contaminants in the oil.
Detergent
Prevents oxidation products (sludge) which have formed in oil from sticking to metal components. May also remove deposits already formed on metallic components. Usually combined with dispersant additive They are also used to neutralise acids which form in the oil, or are introduced as by-products of fuel combustion.
By chemical reaction, oxidation products (sludge) remain soluble in the oil and do not stick to the metal surfaces. Chemically neutralise acids.
Dispersant
Keeps oxidation products separated and suspended in the oil. Retards formation of sludge
By chemical reaction, oxidation product particles are kept small enough to allow them to float in the oil.
Foam Inhibitor
Causes foam to dissipate more rapidly
Protects combination of small bubbles into large bubbles which in turn burst more easily.
Viscosity Index (V.I.) Improver
Reduces rate of change of viscosity with temperature
Additive thickens with increasing temperature thereby preventing oil from thinning out too rapidly
Pour Depressant
Lowers the Pour Point
Keeps small wax crystals apart thus preventing the formation of large crystals which would stop the flow of oil.
Anti-wear agent
Minimizes wear caused by metal-to-metal contact during conditions of mild boundary lubrication e.g. starts and stops
Additive reacts chemically and forms a film on metal surfaces under normal operating conditions
Extreme Pressure (E.P.) Agent
Prevents welding and subsequent wear or seizure of contacting metal parts under extreme or shock load conditions.
When metal-to-metal contact occurs (as under extreme or shock load conditions), the heat generated at the point of contact causes the additive to react chemically with the metal. The new compound formed between the metal surfaces reduces friction and prevents welding or seizure.
Tackiness Agent
Increases the adhesive properties of a lubricant - improves retention and prevents dripping and spattering
High molecular weight compounds are added to the oil thereby increasing its viscosity and improving its adhesive properties.
Emulsifier
Promotes rapid mixing of water and oil resulting in the formation of a stable emulsion (e.g. water-soluble cutting oils)
Reduces interfacial tension and permits intimate mixing of oil and water.
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+ Why special 4T oil is required for 4 Stroke Motor Cycle engines?
The engine oil for four stroke 2 wheelers or 3 wheelers lubricates the engine, the wet clutch and the gears. It is to be noted that engine of these type of vehicles have air-cooled system unlike the passenger car engines which are cooled by water or by a coolant. Furthermore, it should have controlled friction characteristics to take care of the wet clutch requirement. Thus 4T Engine oil is formulated by special additives and base oil.
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+ Why do turbo charged vehicles require special engine oil?
Higher quality engine oil is needed for turbo charged vehicles as they have better fuel combustion thereby increasing thermal load on engine oil and soot production is increased.
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+ What is the difference between diesel engine oil and petrol engine oil?
The performance levels of chemical properties relating to detergent action and dispersion in the two engine oils are different. Accordingly API service classes have two general classifications: ‘S ‘for gasoline engines and ‘C’ for diesel engine. It is possible for an oil to conform to both the gasoline and diesel standards.
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+ What are the reasons for degradation of engine oils?
There are many reasons for degradation of oil,
1 Higher the temperature, the shorter the oil life. Based on the Arhenius Rule, for every 10°C increase in temperature above 40°C, the oil life is halved.
2 The more oxygen from splashing induced by low oil levels the faster the oxidation rate
3 Piston rings having worn out resulting in gaps between the rings & the cylinder. This may result in oil becoming darker/thicker faster.
4 The vehicles are used in overload conditions & dusty atmosphere, etc.
5 Oil filters are not working properly.
6 Fuel dilution resulting in thinner oil.
7 Not using engine oil of correct specification.
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+ What are the possible reasons for excessive oil consumption?
The reasons for excessive oil consumption may be due to any of the following reasons:
1 Some of the many points where external oil leaks may occur include: oil lines, crankcase drain plug,
oil pan gasket, valve cover gasket, oil pump gasket, fuel pump gasket, timing case cover and
camshaft bearing seal.
2 When piston rings are broken or are worn to such an extent that the correct tension
and clearances are not maintained, they will allow oil to be drawn into the
combustion chamber on the intake stroke and hot gases of combustion to be blown
down the cylinder past the piston on the power stroke. Both of these actions will
result in burning and carboning of the oil on the cylinders, pistons and rings.
3 Thinning of the oil due to fuel dilution.
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+ How bad quality fuels effect the performance of engines oil?
Improper combustion of bad quality or adulterated fuel causes abnormal increases in load on the engine which in turn affects the performance of engine oil. Further the byproducts of improper combustion goes into sump thus soot buildup will take place which effect the additives property thereby effecting the overall performance of engine oil.
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+ When do we change the oil?
Oil should be changed as per the equipment manufacturer’s recommendation after fixed hours of operation or after fixed kms. of running, provided the right quality of the oil is used as suggested by the equipment manufacturer. These change periods are established after extensive bench tests & field trials.
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+ How to judge when the oil needs to be changed?
The best way to judge whether the oil’s life is exhausted is to test a sample in the lab. If the TBN has decreased a lot from its starting value and/or the viscosity has increased or decreased substantially, the oil needs to be changed. Since it is not possible to test the oil in the field, it is suggested to look into the following warning signal:
Colour - oil has turned black. This could be due to excessive oil oxidation or heavy contamination of the oil with soot.
Smell - oil emits a burnt odour. This is caused due to dilution of the oil by fuel seeping into the oil circulation system. The oil tends to become less viscous and smells burnt.
Oil’s viscosity - increased or decreased substantially (judged by rubbing the oil between the fingers). Oil’s viscosity increases substantially due to excessive oil oxidation or heavy contamination of the oil with soot and decreases substantially due to dilution of the oil by fuel seeping into the oil circulation system.
Water contamination in the oil - if the oil crackles on heating there is water in oil and if contamination is high, the oil’s colour will also change.
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+ What are the functions of Coolant?
An engine coolant is a heat transfer fluid designed to remove excess heat from an internal combustion engine. It also serves to prevent freezing and most importantly protection from corrosion. An operating engine typically converts only one third of the energy derived through the combustion of fuel into work that moves the vehicle. The other two thirds is converted into heat, of which one third goes out with the exhaust. This leaves the remaining third in the engine block, necessitating the need for a coolant to adsorb this heat, transport it to the radiator and dissipate it into to the environment. Through the removal of this heat by the coolant fluid, the engine is able to operate in an efficient manner. Therefore engine coolant is a generic term used to describe fluids that remove heat from an engine, in effect “cooling” the engine.
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+ Why does oil separates from grease?
A grease is a semi solid lubricant that consists of a dispersion of a thickening agent in a liquid lubricant. This thickener system can be made up of either simple or complex metal soaps of lithium, calcium, aluminum, barium or sodium, or non-soap such as clay (bentone) or polyurea. The thickener system can be thought of as a sponge that contains a matrix of fibers or platelets with a high surface area forming a dense network of micro-asperities (voids) or fibers. It is in these voids or fiber structure where the base oil and additives are stored until they are needed for lubrication. the grease releases its base oils from the thickener system when it is squeezed or stressed. The stresses a grease encounters can be generated either mechanically or thermally during application or storage.
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+ Different aspects of Fluid deterioration