Getting up-close and personal with engine oil
Getting up-close and personal with engine oil
Arief Hidayat, The Jakarta Post, Jakarta
It is well-known that lubricating oil or grease is critical
for car engines. Its function is similar to blood in the human
body. Oil protects the parts of the car's engine from friction by
covering them with thin layers of lubricant.
There are many brands of lubricant on the market, but, in
general, lubricants consist of three types.
The first is the conventional petroleum or mineral-based
lubricating oil. This lubricant is produced from crude oil.
The next is synthetic oil, which is chemically engineered from
a raw material called Polyalphaolefin (PAO). Although the cost of
producing synthetic oil is higher as the process is more
complicated, such oil has advantages over a petroleum-based
lubricant.
For example, it is still able to flow at very low
temperatures, such as during winter, and it remains stable at
high temperatures (thermal stability). It is also less volatile
so that car owners can use it for longer compared to petroleum-
based oil.
The last type of lubricant is a mixture of petroleum-based and
synthetic oils. The composition is usually 80 percent petroleum
and 20 percent synthetic.
Nowadays, customers demand oil producers that are capable of
not only lubricating the engine's moving parts, but that are also
able to prevent corrosion, provide extra sealing between piston
rings and cylinder walls, and keep the engine cool and clean.
Viscosity Index
The viscosity index is used to measure how thin the oil layer
is and how easy the oil flows. This viscosity index measurement
system is certified by the Society of Automotive Engineers (SAE),
and is also known as the SAE rating.
The SAE rating is usually printed on the oil can. Grades go
from 5W (5-weight) to 50W. A 5W grade means relatively thin and
smooth flowing oil, while a 50W grade shows that the oil is
relatively thick and flows more slowly.
From the grade, we can choose which oil is suitable for the
particular car and environment. A 5W oil is usually suitable for
extreme winter climates, while 10W is good for temperatures of
between 0 and 60 degrees Fahrenheit. A 30W oil is normally used
in the summer, 40W for summer and car engines that are employed
for heavy duties, while 50W is suitable for high speed engines
and long distance trips.
Apart from the oil viscosity grade, one should also check out
the institute that certifies the grade. One of the most prominent
certification bodies is the American Petroleum Institute (API).