Self service

Not everyone can afford to take their motor vehicles to service centres to have them serviced. Find out how you can replace the oil in your motor vehicles as part of a service.

By Roelof Strydom

As part of a vehicle’s service, the oil needs to be replaced to ensure the continued smooth running of the engine. The vehicle’s manual will state which oil is best suited to your car’s engine. Have you ever looked at a bottle of oil and wondered what all the codes, numbers and letters represent? If you have, here it is explained.

Viscosity
According to the Shell South Africa website, “viscosity is a measure of an oil’s resistance to flow”. Let’s take water and honey as an example. Water has a low viscosity compared to honey. This means that at the same temperature, water flows more easily than honey, thus honey has a higher viscosity than water.

Engine oils are all about viscosity. Most engine oils today are multigrade oils. This means they are able to maintain their performance in high and low temperatures.

Take a 5W-40 oil for example; the first number (followed by a ‘W’ which stands for winter) indicates the oil’s viscosity under low temperatures. The second and higher number indicates the oil’s viscosity under higher temperatures.

Multigrade oil’s minimise viscosity differences under temperature variations. Quality oil keeps its viscosity steady under different temperatures and usage conditions for a longer period of time.

The viscosity of an oil is important because an oil with the wrong viscosity can lead to the premature failure of your car’s engine.

If the oil in your car’s engine is too thin it might not create enough of a film between the engine’s moving parts to lubricate them, thus causing wear when the engine’s temperature increases.

However, if the oil is too thick it does not flow correctly and does not transfer the heat away from the engine as it should. The oil can also start to oxidise and deposits and sludge can form.

Read the full article on page 36 of the August 2012 issue.