All about Oils

24th May 2012 by Admin

Should you use synthetic or traditional oil in your car? While the more costly synthetic variety has many benefits, it isn’t necessarily the best choice for every drive. To help you decide which oil to use, we’ve gone back to basics...

What is motor oil made of?

There are three types of modern motor oils:

  1. Mineral oil: Conventional oil made from crude oil, which has undergone certain extraction and chemical treatments in the oil refinery. Mineral oils will never be pure, as they are a mix of thousands of different chemicals.
  2. Synthetics-based oil: Made from relatively pure chemicals and designed for specific performance. The oil is contains many materials, depending on what it’s being used for.
  3. Semi-synthetic/semi-blend: A mixture of mineral and synthetic oil.

All three oil types have been chemically-enhanced to meet the performance needs of the modern car. As a result, the oil may contain additives such as detergents, anti-wear agents, rust and corrosion inhibitors and dispersants for heat.

What does motor oil do?

Here are a few features of engine oil:

  • Lubricant: The oil creates a film between the metal parts of the engine, to protect surfaces from grinding and wear.
  • Coolant: It helps cool the car by absorbing the heat caused by running the engine.
  • Sealant: It seals the space between the piston ring and the cylinder liner to prevent engine power from escaping.
  • Detergent: It helps clean the engine by preventing waste from sticking to the interior.
  • Rust inhibitor: By neutralising the acids produced by engine gases, the oil prevents rust and corrosion.

What motor oil should I use?

If you’re thinking about switching oils, it’s wise to check the recommended viscosity grade in your owner’s manual.

Most engine oils are multi-grade viscosity, such as 10W-30 or 5W-40. This is because when the temperature drops, the oil thickens and becomes less effective at lubricating the engine. At high temperatures, the oil becomes thinner, so it’s harder to protect moving parts. The first number in the grade (e.g. 10 in 10W-30) is the oil’s winter weight, or how it behaves in the cold. The second number (e.g. 30) is the thickness of the oil at 100°C. So 10W-30 oil behaves the same as single grade 10W oil when cold and 30 weight oil when hot. This makes the oil ideal for varying temperatures.

Viscosity additives can be added to mineral oils to achieve this range, while synthetics are made from scratch and can achieve lower ‘W’ ratings.

Why and when do I need to change my motor oil?

Oil deteriorates with regular engine use, making it less effective at lubricating and cooling moving parts. This is usually due to a build-up of contaminants and oil additives being used up, making the engine more vulnerable to corrosion and wear.

Changing the oil regularly can help protect the engine. While carmakers claim that new models only need a service at intervals up to 15,000kms, this only applies if your car is driven in ‘ideal conditions’. Driving short distances, towing a trailer or frequently braking are considered to be ‘adverse conditions’ that are hard on the engine’s oil. In these conditions, the oil can’t heat sufficiently, causing a build-up of fuel and water and, in turn, rust and sludge. Since most of us are likely to regularly drive under these ‘adverse conditions’, regular oil changes are imperative.

Making the change

The oil you use will depend on what the engine is used for and whether you need the improved performance and low-temperature features of synthetic oils. If you’re considering making the switch, speak with a professional.

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