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).