What is a good engine oil?

Remember that marketing slogan ‘Oils ain’t oils’?  

Well, it’s more than just a catchy tagline for an advertising campaign, it’s the truth. 

Just as engines are tuned specifically for the different grades of petrol, the same applies to the type of engine oil that’s best suited to your car. In fact, choosing the right engine oil is even more critical to the performance and long-term reliability of your car’s engine than filling up with the recommended grade of petrol. 

That’s because your oil does a lot of heavy lifting in lubricating and protecting key components and, generally, has to last longer than a tank of fuel. 

So, let’s drill down into the nitty gritty of engine oils and explain the basics and why it’s important to choose the right oil, like one of Supercheap Auto's Best Performing Oils, for your vehicle.

To start with, there are numerous factors that create variations in engine oils, which is why there are so many options to choose from at your local Supercheap Auto store.

The first is viscosity. This is essentially the thickness of the oil. Naturally, oil moves around the engine slower when it is thicker but conversely provides more consistent lubrication.

This is an important factor and determines the numbering system you see on the labels.

The first number – usually indicated on a scale between 0W and 25W - is the thickness when the oil is cold (at -17.8°C or 0°F – the W stands for winter). The lower the number, the thinner the oil is when the engine is started at low temperatures. This allows it to move through the engine quicker and lubricate more components, especially at the top of the engine, faster.

The second number - oil’s viscosity changes as the temperature increases and naturally becomes thinner, which is represented by the second number in the coding system. This is indicated on a scale between 20-60.

As an example, an engine oil labelled 5W-30 is significantly thinner, and will operate more efficiently at lower temperatures, than an engine oil that is graded at 20W-50.

Thinner engine oils are more commonly used in modern vehicles to improve the cold start-up procedure while also helping to increase fuel efficiency by reducing friction inside the engine.

This does not necessarily mean that all cars should use the lightest oil, as environmental conditions will also play an effect on the performance of the oil.

For Australians living in a temperate climate, a middle weight oil is suitable for most vehicles. However, for those living in Alpine regions or southern states that are prone to cold winters, a lightweight oil is recommended during the winter months. Conversely, those living in the hotter parts of the country should choose a heavier oil.

Check the owner’s manual of your vehicle for the recommended oil grade from the manufacturer. This will usually have a table outlining the correct grades of oil for varying climatic conditions.

Also, your driving habits will play a role in choosing the right oil, particularly if you intend to put additional stress on the engine by carrying or towing heavy loads, or regularly undertake high-performance driving like track days.

Oil isn’t a very sexy element of your car. It doesn’t make it sound better or look flashier, and, as such, it’s easy to spend less on the stuff you don’t see.

But while it is important to consider price – especially under the current cost-of-living pressure we’re all facing – remember that investing more now on premium oil has the potential to save you from a big bill later on.

Premium oils are proven to increase long-term reliability through added protection, and will also help improve fuel consumption, cutting down your day-to-day expenses on petrol.

The other major factor that makes one type of oil different from the next is how it is produced. 

There are three main types of oil: mineral, synthetic and blended. 

Mineral oil is natural and made during a refining process of crude oil that is pumped from under the earth’s crust. Mineral oils are generally less expensive but naturally break down over time. 

Synthetic oil is not entirely as the name suggests, as it still uses crude oil as the base product. But the petroleum elements are chemically modified and put back together, which improves its longevity and creates a wider variation in viscosities. 

A blended – or semi-synthetic – oil is a mix of both mineral and synthetic oils, providing users with a more affordable solution than premium synthetic oils with some of the added protection. 

All three types of engine oil feature a cocktail of additives that are designed to improve performance, reduce harmful emissions and protect the internal components of your engine. 

These include friction modifiers, anti-wear agents, detergents and oxidation inhibitors. 

While there are global standards for the minimum amount – and types – of additives required for engine oils, premium oils will usually have more – and higher quality – additives to improve long-term reliability and justify their price. 

You can buy additives separately, like anti-wear treatments and ring seal repairer, but these are generally only applicable to older or high mileage vehicles. 

Diesel engines require a unique type of oil compared to conventional petrol engines. 

Diesel engines produce more soot as part of the combustion process, and therefore require more dispersants and detergents in the oil to break this down. 

Look for the Association des Constructuers Europeens dAutomobile (ACEA) or the American Petroleum Institute (API) certification on the container to ensure the oil meets certain performance and quality standards. 

The ACEA has a four-letter system that determines which oil is suitable for what type of engine. If it is labelled with an A, it is suitable for petrol engines. If it has a B, it can be used in diesel-powered light commercial vehicles with a low-level exhaust gas recirculation (EGR) system. The letter C denotes it can be used in a diesel engine with a Diesel Particulate Filter (DPF) or a three-way catalytic converter. And an E means it is suitable for heavy vehicles such as trucks and earth moving equipment.

Changing your oil regularly is critically important to maintain the long-term reliability and performance of your engine. 

Oil will naturally degrade and burn-up over time, reducing its effectiveness in lubricating the internal components of your engine. It will also collect microscopic elements of metal as components, such the piston rings and cylinder bores, wear down over time, which not only increases its viscosity but also has the potential to clog oil lines and galleys. 

Fresh oil and a clean filter are always better, so check your owner’s manual for the manufacturer’s recommended intervals, and make sure this schedule is adhered to when you have the vehicle serviced.  

Even better, change the oil and filter more regularly at home. It’s a relatively simple task, and Supercheap Auto has all the tools, accessories and parts you need.

Visit your local Supercheap Auto store to talk to an expert about your oil needs, or visit the website. If you’re unsure about what oil is best for your car, try the My Garage feature on the Supercheap Auto website. Enter your car registration number and all compatible engine oils for your vehicle will be displayed.