Lubricating oil

A lubricant is a substance (usually a liquid) introduced between two moving surfaces to reduce the friction and wear between them. A lubricant provides a protective film which allows for two touching surfaces to be separated, thus lessening the friction between them.Lubricants are an essential part of modern machinery. Everything from computer hard disk drives to the Airbus A380 requires lubrication of its moving parts.

Lubricants are generally composed of a majority of base oil (most often petroleum fractions, called mineral oils) and a minority of additives (chemicals). Typically lubricants contain 90% base oil and less than 10% additives.

Non-liquid lubricants include grease, to reducing friction and wear in bearings such as ball bearings, roller bearings or air bearings.

Lubricants perform the following key functions.

  • Keep moving parts apart
  • Reduce friction
  • Transfer heat
  • Carry away contaminants & debris
  • Transmit power
  • Protect against wear
  • Prevent corros
 

Additives (chemicals) are used with base oil to impart desirable characteristics of lubricating oil. Additives are used for reduced friction and wear, increased viscosity, improved viscosity index, resistance to corrosion and oxidation, aging or contamination, etc. A large number of additives are used to impart performance characteristics to the lubricants.

The main families of additives are:

Antioxidants
Viscosity index improvers
Anti-wear
Metal deactivators
Corrosion inhibitors
Rust inhibitors
Friction modifiers
Extreme Pressure
Anti-foaming
Demulsifying / Emulsifying


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Liquified Petroleum Gas - LPG
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Lubricant


Viscosity and Viscosity Index

Viscosity is, simply the measure of an oil's thickness and ability to flow at certain temperatures. Generally, the thicker an oil, the higher its viscosity and the thinner an oil the lower its viscosity. This property of oils is represented with a grade called Viscosity index (VI). The Viscosity Index tells us how much the oil will thin when it is subject to heat. The higher the index, the less an oil will thin when it is subject to heat

Lower numbers indicate thinner oil (low viscosity) and higher numbers indicate thicker oil (high viscosity). The Viscosity Index of an oil determines how it reacts under certain conditions. An oil with a too high viscosity may not pump to the proper parts of your engine especially at low temperatures, and the film may tear at high RPM. An oil with a too low viscosity can lose its film strength at high temperatures.

Choosing Viscosity Grade

The most known engine oil viscosity classifications is SAE (Society of Automotive Engineers).

The SAE classifications characterizes the viscosity at low and high temperature of the lubricant. The grade is given by two numbers separated by the letter W (meaning winter). The first number, followed by W represents the low temperature viscosity, 5W, 10W, 15W, 20W, the lower this number, the more fluid at low temperature the oils, the easier the engine starts. The second number gives the high temperature viscosity: 30, 40, 50. The higher this number, the more viscous the oil when hot.

Below are some examples on choosing engine oil by expected outdoor temperature:

If lowest expected outdoor temperature is:
Typical SAE viscosity grades for passenger cars should be :
0 degrees Celsius (32F)
5W-30, 10W-30, 10W-40, 20W-50
-18 C (0 degree F)
5W-30, 10W-30, 10W-40
below -18 C
5W-30

 

You should change your oil filter at every oil change. The oil filter is a strainer that filters out the solid particles of dirt and metal that are picked up by the circulating motor oil. When the filter becomes clogged, a bypass valve allows these contaminants to continue circulating with the oil in the engine, damaging engine parts and creating sludge.

In any case, it is important to change engine oil after 5,000 Km or at least every six months.


Oil Sludge