Do I change my engine oil or not? Using the correct oil keeps your engine running smoothly. Primarily, oil stops the metal surfaces in your engine from grinding together and wearing, by creating a separating oil film between them. The oil also disperses heat and reduces wear, protecting the engine.
On top of this, good oil prevents dirt build-up and deposits by keeping them in suspension. Motor oil even protects against sludge and fights oxidation, keeping the oil fresh and minimising acids which can cause corrosion. In short, oil matters.
When do I change my engine oil?
Below, we answer some of the most common questions about motor oil:
What is oil viscosity?
Viscosity is an important criterion of any lubricating oil. It is a measure of a fluid’s thickness or resistance to flow. For example, honey is thick and water is thin, so honey has a higher viscosity than water. Oil viscosity needs to suit the right ambient temperatures. If it’s too thick when the engine is cold, it won’t move around the engine. And if it becomes too thin when the engine is hot, it won’t give the right protection to the engine parts.
Optimising an oil’s viscosity, or thickness, helps maximise energy efficiency while avoiding component wear.
Viscosity modifiers increase the viscosity of your oil at high temperature but have little effect on low-temperature viscosity. These enable your oil to flow properly when cold and also to remain thick enough to protect your engine components at high temperatures.
Lower-viscosity grades of oil such as Shell Helix Ultra, make it easier for your engine to start from cold because they present less resistance to moving parts and hence take less power from your engine. This also means that you get enhanced fuel economy.
To find the right oil viscosity for your engine, check your manufacturer’s guidelines and bear in mind the weather conditions you live and drive in. For our recommendation, try our simple
What do the oil numbers mean?
Multigrade oils are those oils that have two numbers on the grade, indicating that the oil is able to maintain engine performance in high and low temperatures. A multigrade lubricant minimises viscosity differences under temperature variations.
The first number on a multigrade oil is normally followed by a W, which stands for winter. This number represents the lubricant’s viscosity under lower temperatures, giving an indication of how the oil will flow in the winter. The lower the first number, the thinner it is at low temperatures.
The second number, which appears after the W, represents the oil’s viscosity under high temperatures. The higher the number, the thicker the oil will stay at high temperatures. Using the correct viscosity for your engine increases engine performance, reduces engine wear and increases fuel efficiency.
In addition, synthetic oils usually have better low and high temperature properties than normal mineral oils. This maintains protection while allowing better fuel economy and cold starting.
