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How Engine Oil Works, Choosing the Right Oil, and More

Imagine driving home after work, and suddenly the ‘Check Engine’ light comes on. Even worse, you start hearing loud knocking and rattling sounds coming from the engine.

These signs are usually an indication that your engine doesn’t have enough lubrication and if left untreated, will eventually tear itself apart.

Most people don’t pay attention to engine oil until it’s too late.

What engine oil do I need? What does engine oil even do in the first place?

For those with little understanding around the operation of car engines; low, old, or degraded motor oil can bring up a lot of questions.

We’ve put together a guide to answer any possible questions regarding engine oils, in order to educate and prepare you for potential motor-oil related issues you may come across in the future.

What Is Engine Oil?

Engine oil, sometimes called motor oil, is a lubricating fluid used in internal combustion engines. If you think of an engine as the heart of a car then engine oil will be the lifeblood of the said ‘heart’.

What Does Engine Oil Do?

A diagram showing the lubrication of an engine with labels

Engine oil was originally only used to lubricate engine parts, reduce friction, cleanse, cool down, and protect the engine. Today, engine oil is expected to do much more than that, especially if it’s synthetic.

The following list is an overview of the various functions of engine oil:

  • Lubrication – Your engine is composed of moving components that require lubrication to reduce the effects of friction such as wear and to ensure that your engine runs smoothly.
  • Prevent overheating – Your engine oil helps to disperse excess heat within your engine by absorbing the heat that is produced during combustion.
  • Inhibits rust – Though it may not completely prevent rust, engine oil can reduce the spread of rust and prevent the corrosion of essential engine components by acting as a detergent, neutralizing the acids that are produced.
  • Acts as a sealant – Engine oil prevents engine power from escaping by sealing the space between the piston ring and the cylinder liner.
A mechanic working on an engine

What Are The Types Of Engine Oil Available?

There are various engine oil types available in the market. The different types of engine oils include; synthetic, semi-synthetic, high mileage, and mineral oils. Motorcycles also require a different type of oil.

  • Synthetic oils – These oils are made artificially in the lab through a range of chemical processes, and are designed to provide enhanced engine performance. You can find the best synthetic oils in our guide here.
  • Mineral oils –these oils come from crude oil that has been refined to remove impurities.
  • Semi-synthetic oils – These kinds of oils are usually a combination of both synthetic and mineral oils.
  • High mileage oils – These oils are just that, oil specially formulated for older engines with high mileage. Need a guide on picking the best high mileage oils? Here you go.

It’s easy to think that mineral oils are the most effective in maintaining engine performance since they’re pure, but it’s actually synthetic oils that are designed to adjust to extreme temperatures and resist heat. Another feature is the antioxidant additives in the oil which help prevent oxidation, making them resistant to degradation.

What are the different grades of oil?

There are basically two figures such as  5w-30, 5w-40, or 10w-40 on each oil bottle regardless of the oil type. These numbers indicate oil’s viscosity.

What do they mean?

According to one of the leading oil manufacturer Castrol:

“The viscosity of oil changes with temperature, therefore multi-grade oils were developed to provide protection across a range of operating temperatures. The SAE (Society of Automotive Engineers) scale shows the viscosity of the oil at both hot and cold temperatures. That’s why the viscosity grade on the oil bottle is made up of two numbers.”

The first number followed by W letter indicates viscosity when it’s cold. The lower the number is, the thinner the oil. At low temperatures, thin oil performs better than thick oil, especially during cold starts.

The second number indicates the oil’s viscosity when the engine is at normal operating temperature. The higher the number is the thicker the oil is. At high temperatures, if the oil becomes too thin, it may not perform as well, and if it’s too thick it creates circulation problems.

We provide SAE Grades Chart below:

An SAE Grades chart showing recommended car engine oils in relation to the outside temperatures (in celcius)

You may think that the oil with the highest differential between these two grades successfully protects the engine at both low and high temperatures. This is not necessarily true, depending on your engine, it may perform better with 0w30 then it would with 0w60.

Engine Oil Maintenance, Change, and life

Most people are unaware of how to maintain the oil in their engines. They’re typically confused by the term “maintenance” in this context. Generally, this refers to ensuring that your oil is doing what it is supposed to do and that your engine is performing in an optimum state.

It is recommended to check your oil at least once a month. This involves checking the level of oil in your engine to know if you require a top-up. If your car is older, this frequency needs to increase. Now you need to know the best method to actually check it.

Most professionals will tell you that it is best to check your oil in the morning before you start your car. This rule of thumb works fine considering the oils had time to settle back into the engine which means the results from the engine check will provide an accurate reading of oil level in the engine.

If you check it after driving around, your results will be less accurate. It’s highly likely you’d get a wrong reading considering since the oils been churned around and haven’t had time to settle.

As you check your oil, you might notice that it appears dirty and darker than when you put it in. Don’t panic. This simply means that the oil is doing its job. So don’t change it just because it looks different.

Cars typically have a dashboard that tells you if your engine oil level is low. Always watch out for this warning light,  it could mean a potential leak in your engine. If this is the case, act fast to avoid serious permanent damage to your engine.

Another important part to check is the oil filter. Since its function is to clean up the oil and get rid of particles within it, it might be clogged up. By cleaning the filter from particles, you’re allowing it to perform at its optimal state. If you’re unsure, you can always have an experienced friend or a mechanic to do it.

Man filling up engine with engine oil

When do I change my engine oil?

This differs depending on manufacturers but the best recommendation is to change it every 6,000-8,000 miles. This will ensure that your oil is at the right level every single time and works just as it’s meant to.

While making the oil change or topping up the oil, make sure you know what the car manufacturer recommends in terms of the type and grade of oil to use for your engine. This information can be easily found in your vehicle handbook.

Two mechanic wrenches on a black background

How do I change my engine oil?

Changing your engine oil is an easy task once you get the hang of it. It only takes around 30 minutes to completely change. You can alternatively go to an experienced friend or mechanic to assist you, but if you prefer to DIY, you’ll need the following tools:

  • Oil filter This is an important part of the engine as it clears up the dirt and particles clogged up in the engine oil. It is recommended to change the filter every second time that you perform an oil change, though some manufacturers will recommend that you change it every time.
  • Oil filter wrench set – The oil filter wrench is the tool you will need to remove the old oil filter.
  • Oil drain (drip) pan – As you change your oil, you are going to need this to avoid dripping the old oil on the ground and creating an oily, dirty mess.
  • Funnel – This will help you to pour in the new oil.
  • Other tools include clean rags, ramps, chucks, safety glasses, work gloves, and a hand cleaner.

Before you change the oil, ensure that your engine is slightly warm. Never do this while the engine is hot or too cold. This is because warm oil drains faster than cold oil and when too hot, the oil will be unsafe to drain. A good tip is to run your engine for a few minutes to let it warm up.

Follow these steps to safely change your oil:

  1. Drive onto ramps – Remove the car keys, apply chucks behind the wheels for safety, put on your safety gear and get started.
  2. Place the oil drip pan below the oil drain plug – If locating the oil drain plug is a bit hard for you, you can always consult the owner’s service manual or Google!
  3. Unscrew the plug by hand – At this point, you have to be careful as the oil may be hot. Push the plug back towards the plate to hold back the oil until when you are ready to let it out.
  4. Drain old oil – Check your service manual for the location of the filler cap and remove it.
  5. Replace oil plug – After old oil has been drained into the drain pan, replace the plug and tighten it by hand then secure with a wrench. Never over tighten the plug.
  6. Remove the oil filter – If you intend to remove the filter, place the drain pan below the old filter then carefully remove the filter using a wrench. Use a rag to clean the filter mounting surface and make sure you remove the gasket from the old filter.
  7. Place the new filter – Lightly lubricate the rubber seals of the new filter before screwing it in by hand. Ensure the seal is properly seated in the filter. Though it may not be necessary to tighten with a wrench, check the filter’s instructions just to be sure.
  8. Add the new oil – Using a clean funnel, pour in the prescribed amount of new oil from the top into your engine. Never overfill. Do not forget to replace the filler cap afterward.
  9. Run the engine – This step helps you to identify any leaks and deal with them immediately. If you do not notice any leaks, you’re good to go. Just shut off the engine then let it rest a few minutes to give the oil time to settle.
  10. Check the oil level – Remove the dipstick, wipe it off, then return it in its slot. Remove it again to check if the oil is up to the “full” mark. If it’s not full, add more oil, but avoid overfilling.

Finish up by removing the chucks and backing off the ramps. Dispose of the old oil and filter properly by taking them to an authorized used engine oil drop-off center or a recycling center.

A person using the oil level testing dipstick

What Engine Oil Do I Need? – Choosing The Correct Engine Oil For Your Car

The quickest and easiest way to determine what engine oil you need is to refer to the vehicle manufacturer’s manual. The manual should indicate the engine oil specification for your particular vehicle.

If you can’t find your user manual, there are online resources available at your disposal to help you decipher which engine oil to use, an example is Castrol Oil Selector

Aside from the recommended engine oil from this specific manufacturer, you’ll also be presented with information about the viscosity (thickness) class of the oil. You can then use this information to choose an alternative brand of engine oil.

It’s highly recommended that you stay within the viscosity range recommended by your car manufacturer.

If all else fails, speak to a certified service expert for your vehicle brand and he will advise you accordingly.

We highly recommend that you seek expert guidance; whether that’s referring to your vehicle’s user or service manual, using an online resource, or working with a certified service expert.

Choosing the wrong type of motor oil for your vehicle could very likely void the terms of your warranty and harm your engine.

What Motor Oil Should I Use – Consequences Of Using The Wrong Motor Oil

In terms of which motor oil to use, you can’t just choose at random. There are certain problems that come with using the wrong type of engine oil for your vehicle. Learning to spot these symptoms can save you a lot of trouble in the long-term.

Oil Leaks

Leaking oil is a common problem when using synthetic oil on high mileage or older cars. Synthetic oil escapes the engine by squeezing through tight areas because it flows differently than conventional oil. The most appropriate oil type for older cars with high mileage is conventional

Synthetic oil may not necessarily damage the engine but switching back to conventional oil should help eliminate the oil leakage.

Hard Start during Cold Weather

If your engine has trouble starting during cold weather, the oil you’re using may be too thick. If the oil is too thick for your engine it will not effectively lubricate it, which causes trouble for the car, especially during cold weather.

Poor Fuel Economy

If the oil is too thick, the pistons and other moving parts may face increased resistance. This may not necessarily damage the engine but will likely lower your current fuel economy. Selecting thinner oil may reverse this.

A speedometer showing the fuel guage

The Smell of Burning Oil

You may notice the smell of burning oil while driving. The smell is usually caused by the oil breaking down due to the hot conditions of the engine. This is usually a problem when using motor oils without high enough viscosity.

Leaking oil referenced above may also cause the burning oil smell.

Problems Encountered With Engine Oil and How to Fix Them

Remember- your engine oil is the blood supply of your car. Any issues related to the engine oil directly affect the engine and could potentially be fatal for the car. Some of the common problems that are faced due to engine oil are:

  • Oil Pump failure – This leads to oil starvation, an issue that is almost always fatal. The oil should be of proper viscosity to ensure it flows to different parts of the engine properly.
  • Dirty oil – This is usually an indicator of a faulty filter. Check your filter and change it if necessary.
  • Low oil pressure – This is more often than not due to low oil levels in the engine. Use the dipstick to assess the situation and if it is within permissible levels, then check for other causes. If you experience low oil pressure during a specific season, then you should check the viscosity factor of the oil you use.
  • Burning oil – This could be due to low viscosity, low quality of oil used, an overheating engine, or low oil pressure. Check the engine for worn-out gaskets and seals and if any, replace them to avoid leaks.

It’s important to fix engine issues as soon as possible, if left untreated they can ultimately create even more problems and result in a large and hefty bill.


Now you know all you need about your car’s blood supply.  Do not hesitate or wait to deal with any issues regarding engine oil and always carry out maintenance checks to ensure your engine is operating at an optimum state. You should also consider researching the best synthetic oil for your car, to increase performance and reduce the likelihood of oil-related fatalities.

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