Engine
Oil and its viscosity
 For
satisfactory lubrication of the engine the oil should possess some
functional properties of which viscosity of oil is one of the most
important properties, as it brings out the oil’s capacity to
lubricate. Viscosity is the measure of oil’s resistance to flow. An
oil’s viscosity is identified by its SAE’s (Society for
Automotive Engineer’s) number. The thinner and oil, lower its
number, e.g. SAE 10 W. The numerical relates to viscosity at particular
temperature and the alphabet ‘W’, indicates the oil’s
suitability for colder temperature. With the viscosity index improver,
the viscosity increses 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 multigrade oils, for
instance ‘20 W40’ shows thinness at low temperature and
thickness at higher temperature.
However, there are other service classification 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. 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 the fuel. Just like any other
subject on cars, the first and the best guide for vehicle owners is to
follow very carefully maintenance o instruction manual provided by the
manufacturers. If one has questions or is unsure about which product to
use, contact the manufacturer of the preferred brand of oil. They are
specialists with extensive knowledge of petroleum chemicals to remove or
ignorance of 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 then be 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
specification sheet that 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
anywhere between 5000 to 15000 kms (or even more) or six months to one
year, whichever is first. At times, due to unusual circumstances, there
may be shorter periods to change the oil especially if one drives short
distances and a lot of switching on and off 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 always safe to have the level of oil indicating on the dipstick
between MIN and MAX marks. One should check the oil level at least once
every two weeks or after every 1000 kms, and specially 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 nearly cosmetic value.
Change of filters is normally recommended with every oil change
considering the impurities of fuel and dusty condition of the country.
It is a good habit to keep engine running at idle for few minutes after
it is started. One should not rev the engine. This allows the oil to
flows all over the moving parts before any load is placed on the engine.
Remember, the maximum wear and tear of the engine takes place when it is
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 pug to know if it is plugged properly.
The care the lubricant manufacturers take in their packaging and
sealing indicates the seriousness of the matter.
Checklist
- Use only recommended engine oil. It
should be in the owners manual and if you are unsure call up the
manufacturer or the dealer.
- Change the engine oil every six
months or five thousand kms, whichever is earlier.
- Make a note of your last oil
change. At the time oil change make sure you use the recommended
lubricants only. Check the packaging of the oil to make sure it is
not spurious.
- Always buy from recognized 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 plaster. If it indicates
low oil do not drive the car till you refresh the engine oil.
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