What’s the Deal With Engine Oil?

By Angela Monroe - April 28, 2021

What’s the Deal With Engine Oil

Engine oil is something all motorists know as the lifeblood of a car. Too much, too little or the wrong type and you can be up for thousands of dollars in repairs.

We take a look at engine oil, what it does and why it’s so important.

Firstly, what do the numbers mean?

oils numbers

5W-40, 15W-30 and so on. Oil seems to have its own language. 

These numbers are ‘grades’ and refer to how ‘runny’ or not the engine oil is – this is measured in viscosity. The hotter the oil, the runnier or the higher the viscosity. The Society of Automotive Engineers (SAE) is responsible for this grading system. The lower the number, the more easily it will flow.

Think of it like honey

You put a jar of honey in the fridge, it’ll be really thick and hard to spread, microwave it and it’s much thinner. That principle applies to engine oil. 

The ‘W’ stands for ‘winter’ and the number before it represents the flow or viscosity of the oil when it is cold. When engine oil is cold, it flows slower – or is a thicker liquid. A 10W-40 oil will flow better than a 15W-40.

The second number, the ‘40’ in the example above refers to the viscosity of the engine oil when it’s hot or at operating temperature.

Engine oil grade examples

Engine oil grade

0W-20 engine oil is very thin or runny and can operate in very cold climates. Typically you won’t see this kind of oil in Australia.

15W-40 engine oil is rated for most Australian conditions. It won’t get too thick on cold mornings and won’t be too thin in summer. Of course, car engines are designed for specific engine oil grades so always check your owner’s manual.

10W-60 engine oil has a large temperature range. Often, high performance racing cars use this as their engines operate in extreme conditions and under a lot of stress.

Synthetic engine oils

Synthetic engine oils

Engine oil can be a natural product – or with minimal refinement. It can also be completely synthetic – or with a lot of refinement. This is similar to fuel too.

Generally, synthetic engine oil offers more protection in a car’s engine as it has been specially formulated. This makes it cost more.

Unlike food where ‘organic and natural’ is typically healthier, car engines generally like something refined by people.

Mineral engine oil is natural and usually cheaper. It’ll need to be replaced more often.

Semi-synthetic engine oil contains mineral and synthetic oils.

Fully-synthetic engine oil is refined and often contains additives such as anti-wear properties to protect engines.

Some engine oil symptoms

oils problems

Oil leaks

Using synthetic oil in an older car or a car with high mileage can cause leaks. This can often be because thinner oils are able to squeeze through gaps that newer engines haven’t yet formed. Other than stains on a driveway, owners of these vehicles should keep a close eye on the engine level.

Burning oil smell

This is pretty common. If you’ve ever driven up a steep hill with a lot of other traffic around, you’ll often smell it – especially if it’s a high speed. It can be a cause of summer breakdowns as some cars struggle with oil leftover from winter.

This is often because of oil leaks on hot engine parts or a result of using the wrong oil. At extreme temperatures, oil can break down.

Ticking sound in cold weather

Usually on startup when the engine is cold. This means the oil is too thick to properly lubricate the engine. The noise will typically stop when the engine warms up. This is often caused by using the wrong oil grade.

Driving a car with no engine oil

oil seize

What could be considered ‘car murder’, driving a car without any engine oil will quickly (within minutes, if not seconds) destroy an engine.  It’ll likely trigger a ‘check engine’ light before getting completely empty.

The oil’s job is to help fast moving parts slide past one another without friction or grinding together. In other words, engine oil lubricates moving parts.

Without oil, a car engine will seize. That means the moving parts are stuck together. Furthermore, this can generate a lot of heat so burning smells, smoke or even fire is possible.

The right engine oil

clean engine

The right oil is the grade and type listed by the vehicle’s manufacturer. Just like knowing when your car’s brakes need replacing, it is important to keep an eye on engine oil.

Car manufacturers spend hundreds of millions of dollars and years of time developing an engine – that means a lot of testing to make sure their investment pays off. It also explains why using the recommended oil is a good idea.

Angela Monroe
Angela Monroe is the Community Manager at The Positive Group, specialising in giving people the information that they need when they need it, and putting you on the path to a fair financial future. She has 8 years of experience in helping Australians find the right finance solutions, and regularly contributes articles to empower Australians with the knowledge they need to become financially healthy.


No comments yet.

Sorry, the comment form is closed at this time.

  • Quick Quote

  • Related Posts