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ENGINE OIL

It is anoilused forlubricationof variousinternal combustion engines. The main function is to

lubricatemoving parts; it also cleans, inhibitscorrosion, improves sealing, andcools the engineby

carryingheataway from moving parts. In engines, there are parts which move against each othercausingfrictionwhich wastes otherwise usefulpowerby converting the energy to heat. Contactbetween moving surfaces alsowearsaway those parts, which could lead to lower efficiency and

degradation of the engine. This increases fuel consumption, decreases power output and can lead to

engine failure.

Lubricating oil creates a separating film between surfaces of adjacent moving parts to minimize direct

contact between them, decreasing heat caused by friction and reducing wear, thus protecting the

engine. In use, motor oil transfers heat throughconvectionas it flows through the engine by means of

air flow over the surface of the oil pan, an oil cooler and through the build up of oil gases evacuated by

thePositive Crankcase Ventilation(PCV) system.

In petrol (gasoline) engines, the toppiston ringcan expose the motor oil to temperatures of 160 C

(320 F). In diesel engines the top ring can expose the oil to temperatures over 315 C (600 F). Motor

oils with higherviscosityindices thin less at these higher temperatures.

Coating metal parts with oil also keeps them from being exposed tooxygen, inhibitingoxidationat

elevated operating temperatures preventingrustorcorrosion.Corrosion inhibitorsmay also be added

to the motor oil. Many motor oils also havedetergentsanddispersantsadded to help keep the engine

clean and minimizeoil sludgebuild-up. The oil is able to trap soot from combustion in itself, rather than

leaving it deposited on the internal surfaces. It is a combination of this, and some singeing that turns

used oil black after some running.

COMPOSITION OF ENGINE OIL

Most motor oils are made from a heavier, thickerpetroleumhydrocarbonbase stock derived fromcrude

oil, with additives to improve certain properties. The bulk of a typical motor oil consists

ofhydrocarbonswith between 18 and 34carbonatomspermolecule.[6]One of the most important

properties of motor oil in maintaining a lubricating film between moving parts is itsviscosity. The

viscosity of a liquid can be thought of as its "thickness" or a measure of its resistance to flow. Theviscosity must be high enough to maintain a lubricating film, but low enough that the oil can flow

around the engine parts under all conditions. Theviscosity indexis a measure of how much the oil's

viscosity changes as temperature changes. A higher viscosity index indicates the viscosity changes less

with temperature than a lower viscosity index.

Another manipulated property of motor oil is itsTotal Base Number(TBN), which is a measurement of

the reservealkalinityof an oil, meaning its ability to neutralize acids. The resulting quantity is

http://en.wikipedia.org/wiki/Oilhttp://en.wikipedia.org/wiki/Oilhttp://en.wikipedia.org/wiki/Oilhttp://en.wikipedia.org/wiki/Lubricationhttp://en.wikipedia.org/wiki/Lubricationhttp://en.wikipedia.org/wiki/Lubricationhttp://en.wikipedia.org/wiki/Internal_combustion_enginehttp://en.wikipedia.org/wiki/Internal_combustion_enginehttp://en.wikipedia.org/wiki/Internal_combustion_enginehttp://en.wikipedia.org/wiki/Moving_partshttp://en.wikipedia.org/wiki/Moving_partshttp://en.wikipedia.org/wiki/Moving_partshttp://en.wikipedia.org/wiki/Corrosionhttp://en.wikipedia.org/wiki/Corrosionhttp://en.wikipedia.org/wiki/Corrosionhttp://en.wikipedia.org/wiki/Engine_coolinghttp://en.wikipedia.org/wiki/Engine_coolinghttp://en.wikipedia.org/wiki/Engine_coolinghttp://en.wikipedia.org/wiki/Heathttp://en.wikipedia.org/wiki/Heathttp://en.wikipedia.org/wiki/Heathttp://en.wikipedia.org/wiki/Frictionhttp://en.wikipedia.org/wiki/Frictionhttp://en.wikipedia.org/wiki/Frictionhttp://en.wikipedia.org/wiki/Motive_powerhttp://en.wikipedia.org/wiki/Motive_powerhttp://en.wikipedia.org/wiki/Motive_powerhttp://en.wikipedia.org/wiki/Wearhttp://en.wikipedia.org/wiki/Wearhttp://en.wikipedia.org/wiki/Wearhttp://en.wikipedia.org/wiki/Convectionhttp://en.wikipedia.org/wiki/Convectionhttp://en.wikipedia.org/wiki/Convectionhttp://en.wikipedia.org/wiki/PCV_valvehttp://en.wikipedia.org/wiki/PCV_valvehttp://en.wikipedia.org/wiki/PCV_valvehttp://en.wikipedia.org/wiki/Piston_ringhttp://en.wikipedia.org/wiki/Piston_ringhttp://en.wikipedia.org/wiki/Piston_ringhttp://en.wikipedia.org/wiki/Viscosityhttp://en.wikipedia.org/wiki/Viscosityhttp://en.wikipedia.org/wiki/Viscosityhttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Oxidationhttp://en.wikipedia.org/wiki/Oxidationhttp://en.wikipedia.org/wiki/Oxidationhttp://en.wikipedia.org/wiki/Rusthttp://en.wikipedia.org/wiki/Rusthttp://en.wikipedia.org/wiki/Rusthttp://en.wikipedia.org/wiki/Corrosionhttp://en.wikipedia.org/wiki/Corrosionhttp://en.wikipedia.org/wiki/Corrosionhttp://en.wikipedia.org/wiki/Corrosion_inhibitorhttp://en.wikipedia.org/wiki/Corrosion_inhibitorhttp://en.wikipedia.org/wiki/Corrosion_inhibitorhttp://en.wikipedia.org/wiki/Detergenthttp://en.wikipedia.org/wiki/Detergenthttp://en.wikipedia.org/wiki/Detergenthttp://en.wikipedia.org/wiki/Dispersanthttp://en.wikipedia.org/wiki/Dispersanthttp://en.wikipedia.org/wiki/Dispersanthttp://en.wikipedia.org/wiki/Oil_sludgehttp://en.wikipedia.org/wiki/Oil_sludgehttp://en.wikipedia.org/wiki/Oil_sludgehttp://en.wikipedia.org/wiki/Petroleumhttp://en.wikipedia.org/wiki/Petroleumhttp://en.wikipedia.org/wiki/Hydrocarbonhttp://en.wikipedia.org/wiki/Hydrocarbonhttp://en.wikipedia.org/wiki/Hydrocarbonhttp://en.wikipedia.org/wiki/Crude_oilhttp://en.wikipedia.org/wiki/Crude_oilhttp://en.wikipedia.org/wiki/Crude_oilhttp://en.wikipedia.org/wiki/Crude_oilhttp://en.wikipedia.org/wiki/Hydrocarbonhttp://en.wikipedia.org/wiki/Hydrocarbonhttp://en.wikipedia.org/wiki/Hydrocarbonhttp://en.wikipedia.org/wiki/Carbonhttp://en.wikipedia.org/wiki/Carbonhttp://en.wikipedia.org/wiki/Atomhttp://en.wikipedia.org/wiki/Atomhttp://en.wikipedia.org/wiki/Atomhttp://en.wikipedia.org/wiki/Moleculehttp://en.wikipedia.org/wiki/Moleculehttp://en.wikipedia.org/wiki/Motor_oil#cite_note-6http://en.wikipedia.org/wiki/Motor_oil#cite_note-6http://en.wikipedia.org/wiki/Motor_oil#cite_note-6http://en.wikipedia.org/wiki/Viscosityhttp://en.wikipedia.org/wiki/Viscosityhttp://en.wikipedia.org/wiki/Viscosityhttp://en.wikipedia.org/wiki/Viscosity_indexhttp://en.wikipedia.org/wiki/Viscosity_indexhttp://en.wikipedia.org/wiki/Viscosity_indexhttp://en.wikipedia.org/wiki/Total_Base_Numberhttp://en.wikipedia.org/wiki/Total_Base_Numberhttp://en.wikipedia.org/wiki/Total_Base_Numberhttp://en.wikipedia.org/wiki/Alkalinityhttp://en.wikipedia.org/wiki/Alkalinityhttp://en.wikipedia.org/wiki/Alkalinityhttp://en.wikipedia.org/wiki/Alkalinityhttp://en.wikipedia.org/wiki/Total_Base_Numberhttp://en.wikipedia.org/wiki/Viscosity_indexhttp://en.wikipedia.org/wiki/Viscosityhttp://en.wikipedia.org/wiki/Motor_oil#cite_note-6http://en.wikipedia.org/wiki/Moleculehttp://en.wikipedia.org/wiki/Atomhttp://en.wikipedia.org/wiki/Carbonhttp://en.wikipedia.org/wiki/Hydrocarbonhttp://en.wikipedia.org/wiki/Crude_oilhttp://en.wikipedia.org/wiki/Crude_oilhttp://en.wikipedia.org/wiki/Hydrocarbonhttp://en.wikipedia.org/wiki/Petroleumhttp://en.wikipedia.org/wiki/Oil_sludgehttp://en.wikipedia.org/wiki/Dispersanthttp://en.wikipedia.org/wiki/Detergenthttp://en.wikipedia.org/wiki/Corrosion_inhibitorhttp://en.wikipedia.org/wiki/Corrosionhttp://en.wikipedia.org/wiki/Rusthttp://en.wikipedia.org/wiki/Oxidationhttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Viscosityhttp://en.wikipedia.org/wiki/Piston_ringhttp://en.wikipedia.org/wiki/PCV_valvehttp://en.wikipedia.org/wiki/Convectionhttp://en.wikipedia.org/wiki/Wearhttp://en.wikipedia.org/wiki/Motive_powerhttp://en.wikipedia.org/wiki/Frictionhttp://en.wikipedia.org/wiki/Heathttp://en.wikipedia.org/wiki/Engine_coolinghttp://en.wikipedia.org/wiki/Corrosionhttp://en.wikipedia.org/wiki/Moving_partshttp://en.wikipedia.org/wiki/Internal_combustion_enginehttp://en.wikipedia.org/wiki/Lubricationhttp://en.wikipedia.org/wiki/Oil

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determined as mg KOH/ (gram of lubricant). Analogously,Total Acid Number(TAN) is the measure of a

lubricant'sacidity. Other tests includezinc,phosphorus, orsulfurcontent, and testing for

excessivefoaming.

Base Oil> 85% -100%

Mineral Oils (Paraffinic, Naphthenic), Synthetic Hydrocarbons (PAO, Alkylates) and other Synthetic

Compounds (Esters, Polyglycols, etc.)

Additives 0% - 15%

Oxidation inhibitors, Corrosion and Rust preventives, Metal deactivators, AW/EP agents, Tackifiers, Solid

lubricants (MoS2, Graphite), Friction modifiers, Dyes etc.

NOMENCLATURE:

As oils heat up, they generally get thinner. Single grade oils get too thin when hot for most

modern engines which is where multigrade oil comes in. The idea is simple - use science

and physics to prevent the base oil from getting too thin when it gets hot. The number

before the 'W' is the 'cold' viscosity rating of the oil, and the number after the 'W' is the

'hot' viscosity rating. So a 5W40 oil is one that behaves like a 5-rated single grade oil when

cold, but doesn't thin any more than a 40-rated single grade oil when hot. The lower the

'winter' number (hence the 'W'), the easier the engine will turn over when starting in cold

climates. There's more detail on this later in the page under both viscosity, and SAE ratings.

http://en.wikipedia.org/wiki/Total_Acid_Numberhttp://en.wikipedia.org/wiki/Total_Acid_Numberhttp://en.wikipedia.org/wiki/Total_Acid_Numberhttp://en.wikipedia.org/wiki/Acidityhttp://en.wikipedia.org/wiki/Acidityhttp://en.wikipedia.org/wiki/Acidityhttp://en.wikipedia.org/wiki/Zinchttp://en.wikipedia.org/wiki/Zinchttp://en.wikipedia.org/wiki/Zinchttp://en.wikipedia.org/wiki/Phosphorushttp://en.wikipedia.org/wiki/Phosphorushttp://en.wikipedia.org/wiki/Phosphorushttp://en.wikipedia.org/wiki/Sulfurhttp://en.wikipedia.org/wiki/Sulfurhttp://en.wikipedia.org/wiki/Sulfurhttp://en.wikipedia.org/wiki/Foamhttp://en.wikipedia.org/wiki/Foamhttp://en.wikipedia.org/wiki/Foamhttp://www.carbibles.com/engineoil_bible_pg2.html#viscosityhttp://www.carbibles.com/engineoil_bible.html#saehttp://www.carbibles.com/engineoil_bible.html#saehttp://www.carbibles.com/engineoil_bible_pg2.html#viscosityhttp://en.wikipedia.org/wiki/Foamhttp://en.wikipedia.org/wiki/Sulfurhttp://en.wikipedia.org/wiki/Phosphorushttp://en.wikipedia.org/wiki/Zinchttp://en.wikipedia.org/wiki/Acidityhttp://en.wikipedia.org/wiki/Total_Acid_Number

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Which one is better: multi-grade engine oil or mono-grade engine oil:

Multigrade oil is oil whose viscosity properties have been changed artificially in order to slow

down its rate of change of viscosity with temperature. Thus such oil tends to be thinner at

low temperatures and thicker at high temperatures than monograde oil.

There are several benefits one may expect of multigrade oil.

1. When a vehicle is at rest for a few hours, all the engine oil comes down to the oilsump. Thereafter, when the vehicle is started, there is a certain time (probably only

microseconds) before the oil reaches all the parts of the engine once again. Since

the multigrade oil is thinner at low temperatures, it reaches all parts of the engine

quicker than monograde oil and hence, reduces wear to that extent.

2. Generally, it has been observed that use of multigrade oils enables better fueleconomy of 1.5% - 3%.

3. Multigrade oil offers better protection to the engine at high temperatures thanmonograde oil, since it is thicker than the monograde oil at temperatures above

100OC. This is so even if the multigrade oil is thinner than the monograde oil at

temperatures below 100OC. This property of multigrades also reduces oil

consumption.