A vehicle
requiring proper maintenance, for functioning well is a
fact which every owner is aware of yet overwhelming majority
of them are not conscious of certain vital subjects of maintenance
like lubricants. Very few vehicle owners know what lubricants
are, what is its main functions and what kind of lubricants
they should use. A modern contemporary three box car has
thousands of parts and well over 1000 parts of them are
synchronised to move together within extreme tolerances.
Under
such demanding conditions the role of lubricants can never
be over emphasised. Depending on his or her level of awareness,
a vehicle owner might be thoughtfully caring or damaging
very seriously his or her machine and perhaps loose its
complete value. Nothing much happens if you run out of the
fuel and get stranded but if you are running on low or wrong
engine oil you would never know the extent of damage you
to your vehicle.
The
main purpose of lubricants is to lubricate the vehicle to
reduce friction and providing smooth, trouble free nereased
length of time. A lubricant is a blend of base oils and
performance-enhancing additives as required by engine, gear
box and other application areas. At the refinery, the crude
oil is refined into gasoline, diesel, kerosene, LPG, naphtha
and base stocks (Lube). This base stock is further processed,
blended and strengthened with required properties to make
different kind of lubricants. Of all the lubricants engine
oil is the most important. lubricants for gasoline and diesel
engine are different as the load, cycles and fuels are different.
The oil in an engine does more than just reduce friction
between its moving parts. it also helps to seal the high-
pressure combustion gases inside the cylinders, to impede
the corrosion of metal parts, to absorb some of the harmful
by-products of combustion, and to transfer heat from one
part of the engine to another. Combustion of rich air-fuel
mixture during starting, idling and warm up form products
that contaminate the oil and form deposits. These deposits
in the form of varnish, sludges, soot and carbon, interfere
with the proper engine operation. The engine oil keeps all
the deposit forming material in suspension and gets rid
of them by oil filter, or draining out at proper intervals.
Engine oil is stored in the oil pan or sump at the bottom
of the engine. A pump forces the oil through a filter and
then through a series of passages and galleries to lubricate
the engine's moving parts. The flow of oil also coois these
pads. Rapidly moving engine parts actually float on a thin
film of oil and never make contact with one another. This
is called hydrodynamic lubrication, and usually begins when
an engine reaches the idle speed. Most engine wear occurs
when a cold engine is first started, before the oil reaches
its normal operating pressure and flow. Diesel Engine Lubricating
Oil The main function of lubricant for diesel engine are
the same as mentioned for gasoline engine. As the load in
diesel engine is much higher it should have adequate antiwear
properties. Diesel fuel contains a high level of Sulphur
which burns to form oxides of sulphur, which in turn in
the presence of water, forms sulphur acids resulting in
high corrosion of engine pads. Hence the need for alkalinity
reserve in the oil which is represented by its TBN or Total
Base Number. Generally, the higher the TBN value, more the
alkalinity reserve or acid neutralising capacity the oil
contains. Synthetic Oil The advent of synthetic oil more
than fifty years back opened up vastly improved and new
alternative lubricant to mineral oil. But being very expensive
it is confined to arcane world of motor spods and used for
high performance cars. They are also widely used in developed
countries for number of reasons like improved overall engine
performance, low oil consumption, long drain periods, less
engine wear, improved engine cleanliness and faster starting.
Taking into consideration the price tag and its efficacy,
the option is left for consumer's discretion. Additives.
What they do Plain mineral oils cannot provide all the necessary
functional properties which an engine requires. These plain
mineral oils need fortification which chemicals/additives
which when used in small quantities, import or enhance the
desirable functional properties. Some of the types and reasons
for their use are as follows: - Dispersants:- Keeps sludge,
carbon and other deposit- precursors suspended in oil. Detergents:
- Keeps the engine parts clean from deposits. Rust/Corrosion
inhibitors:- Neutralises acids, prevents corrosion from
acid attack. Oxidation inhibitors:- Prevents or controls
oxidation of oil, formation of varnish, sludge and corrosive
compounds, limit viscosity increase. Extreme pressure (EP):-
Anti wear and friction modifiers. Forms protective film
on engine pads, reduces wear and tear. Metal deactivators:-
Forms surface films so that metal surface do not catalyse
oil oxidation. Four Point Depressant..- Lowers freezing
point of oils assuring free flow at lower temperatures.
Anti- foamants:- Reduces foam in crank case and blending.
Oils and their Viscosity For satisfactory lubrication of
the engine the oil should possess some functional properties
of which viscosity of an oil is one of the most important
properties as it bring out the oil capacity to lubricate.
Viscosity is the measure of an oil's resistance to flow.
An oil's viscosity (thickness) is identified by its SAE-
Society of Automotive Engineers, number. The thinner an
oil, lower it's number e.g. SAE 10 W. The numericals relates
to viscosity at particular temperature and letter 'W"
indicates the oil's suitability for colder temperature.
With the viscosity index improver, the viscosity increases
at higher temperature and at lower temperature it does not
increase significantly thus achieving optimum viscosity
at lower and higher temperature. Such oils are called naultigrade
oil like for instance 20 W40 showing thinness at low temperature
and thickness at high temperature. However, there are other
service classifications of oil apart from viscosity, developed
by API - American Petroleum Institute which indicates service
characteristics. It is graded on a scale from SA (the lowest)
to SJ (the highest) for gasoline engines, it is graded on
a scale from CA to CG 4. Both the recommendations for viscosity
and service classification can be found on label of the
oil container. As we are extremely affected by the prices,
quality and other vagaries of the fuel available, we tend
to forget that caring to use correct type of oil is perhaps
more important than fuel. Just like any other subject on
cars, the first and best guide forvehicle owners isto follow
very carefully maintenance or instruction manual provided
by the manufacturers. If one has questions or unsure about
which product to use, contact the manufacturer of the preferred
brand of oil. There are specialist with extensive knowledge
of petroleum chemicals to remove any doubts or ignorance
for good. Of course there are always proficient hands to
help you at your own dealer's workshop. The quality of oil
is determined by SAE viscosity grades and by API service
classifications. It should be then matched with the recommendation
in the service manual and with the label on the oil container
having SAE and API ratings. One can always refer to the
specifications sheet which gives detail on product performance.
This enables one to understand why certain brands exceed
by large margin the safety and performance level set by
SAE and API standards by a higher quality of oil and viscosity
range- something which is not necessary for every car- but
yes, for high performance and luxury cars. Oils should always
be changed at the intervals recommended by the maintenance
manual. These days the drain life of an engine oil is any
where from 5000 to 15000 kms (or even more) or six months
to one year, which ever is first. At times, due to unusual
circumstances, there may be shorter periods to change the
oN especially if one drives short distances and a lot of
switching on and oft of the engine is involved. The condition
of the engine oil can also be felt by the slickness of the
oil. But your fingers and thumb will need lot of experience
to know that. Your trusted service man can always help you.
It is always safe to have the level of oil indicating on
the dipstick between MIN and MAX marks. One should check
the oil level atleast once every two weeks or after every
1000 kms, and especially before a long journey. It is dangerous
for the engine to run with low or no engine oil. And remember
the colour of the oil has nothing to do with its ratings
or performance, it has merely cosmetic value. Change of
filters is normally recommended with every oil change considering
the impurities of fuel and dusty conditions of the country.
It is good habit to keep engine running at idle for few
minutes after its started. One should not rev the engine.
This aliows the oil to flow all over the moving parts before
any load is placed on the engine. Remember, the maximum
we and tear of the engine takes piace when it i started
for the first time of the day. Always purchase replacement
oils from trusted and established source and make sure the
oil and the filter is changed in your presence. Recheck
the drain plug to know if it's plugged properly. The care
the lubricant manufacturers takes in their packings and
sealing indicates the seriousness of the matter and oil
for engine is serious matter.
CHECKLIST
-
Use
only recommended engine oil. It should be in the owner's
manual and if you are unsure call up the manufacturer
or the dealer.
-
Change
engine oil every six months or 5000 kms whichever is
earlier.
-
Make
a note of your last oil change. At the time of oil change
make sure you use the recommended lubricant only.
-
Cheek
the packaging of the oil to make sure it is not spurious.
-
Always
buy from recognised dealers and outlets.
-
Change
oil filter at the time of an oil change.
-
Never
drive your vehicle if the engine oil level is low or
it does not have engine oil.
-
Most
cars have an indicator for engine oil on the dashboard
instrumentation cluster. If it indicates low oil do
not drive the car till you refill the engine oil.
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