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Engine Oil – The Only Guide You’ll Ever Need

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Engine oil is literally gold for your car engine! It keeps it performing at its best.
Engine oil keeps the engine performing at its best. Image courtesy of UltraLube.

Engine oil is a lubricant that:

  1. Protects your car engine from wear and tear,
  2. Prevents it from overheating, and
  3. Improves engine performance by reducing friction.

Poor engine lubrication not only increases your fuel consumption, but also wear out your engine – which will costs a bomb to repair.

It’s true!

Whether you love your car or just want to lower your petrol bill, you should take a good look at your engine oil.

We’re going to discuss the following topics about engine oil, feel free to skip ahead to what tickles your fancy.

What is engine oil?

Flashy container, 5W-30 and synthetic. These are the things we associate with engine oil!
Flashy container, 5W-30 and synthetic. These are the things we associate with engine oil!

Behold! These are engine oil.

I’m sure you’ve recognized it from the picture already. Without a doubt, it is the most commonly serviced vehicle fluid in our car.

The oil are golden in color and look exactly like cooking oil, except we don’t cook with it – we pour it into our engine to keep it well-lubricated.

Engine oil come in a plastic container like above. They can come in different sizes, such as…

  • 1-litre bottles,
  • 4-litres bottles, and
  • 5-litres bottles.

The 4-litres bottles are the most common.

Engine oil is everywhere! You can find them at most petrol station and spare parts shop.

Nowadays, you can even get them from online e-commerce platforms like Lazada and Shoppee!

There are three different grades of engine oil and they are generally priced as follows:-

  • Mineral Oil = RM 15 – RM 30 / Litre
  • Semi-Synthetic = RM 30 – RM 50 / Litre
  • Fully Synthetic = RM 50 ++ / Litre

Why do we need engine oil?

Yeah, we know that it lubricates the engine. But why do we need that lubrication in the first place? Can’t our engine just run without it?

Yes, it can. But it won’t last very long!

If you’re dying to find out, Car Throttle emptied the engine oil from their Mercedes C180 year 1994 and tried running it.

The results? Not very good.

Don’t try this at home.

Our car engine produces explosions that moves our engine piston up and down.

It works like this.

  • The bottom part of the pistons are connected to the crankshaft.
  • So when the explosions pushes the pistons up and down, it turns the crankshaft.
  • When the crankshaft turns, we have this rotational energy that we harvests as power to move our car.

So if you really think about it… 

Our cars are running on constant tiny explosions!

We don’t feel the explosions but it doesn’t mean it’s harmless.

With such extreme operating temperature and moving metal parts grinding against each other, it can never spell good news.

That is exactly why we need engine oil. Here are the 3 main reasons.

Reason #1: Reduces engine wear and tear

Engine oil reduces friction between the metal parts of an internal combustion engine.

When the friction is lower, we get lesser metal-to-metal contact.

This means lesser wear and tear which helps to extend our car engine life.

Reason #2: Act as a cooling medium

Not only that, engine oil also acts as a cooling medium.

When we drive our car, our engine makes tiny explosions to move the car. It will get very hot and will overheat if we don’t do anything about it.

That’s where engine oil comes in.

Engine oil will flow around the engine and take the heat away from the engine.

It absorbs the heat, keeping engine temperature between 95 degree celsius and 105 degree celsius.

Obviously, the engine oil will become hot. Our car radiator helps to cool them before they head back in to absorb more heat.

I guess you can say that… Engine oil is cool.

Reason #3: Prevents sludge and dirt

Just like any other liquid, engine oil move and slush around the engine.

Imagine the tidal waves of the sea hitting a rock. It splashes and cleans the rock.

Engine oil does the same thing, except with engine.

It helps to collect the tiny particles and dirt found within the engine.

When they’re done collecting the dirt, it flows through an oil filter which filters out these unwanted particles.

Then, it goes back into the engine again to do more cleaning.

There are so many types and brands of engine oil! What’s the difference?

When we try to compare engine oil, there are four criterias that we have to look at.

  • Grade of engine oil
  • Additives
  • Viscosity rating
  • Service Category

If it helps, imagine it like a bowl of soup!

The base stock is the soup base (fish stock / chicken stock) and it makes up the body of the soup. Whatever core ingredient you use here will affect the overall quality of the soup. The grade of engine oil is the same thing.

The additives are like seasoning – think salt and pepper. It enhances the flavor of the soup.

Viscosity rating is just a grumpy judge telling you how thick or thin your soup is.

Finally, service category is who the soup is meant for: kids or grown adults.

Criteria #1: Grade of Engine Oil

Virtually all commercial engine oil is made from base stock and additives.

If we measure by weight, base stock generally makes up 95% of the engine oil while additive makes up the remaining 5%.

The base stock that we use will determine the grade of engine oil to be either:

  • mineral oil based
  • semi-synthetic
  • fully-synthetic

If the base stock is made from refining crude oil, then it is a mineral oil.

If chemical engineers take the mineral oil and improve it further it in the lab, then it’s a synthetic oil.

Semi-synthetic is a blend of the two, usually consists of 70% mineral oil and 30% synthetic oil.

The way we process the base stock changes three things: (i) concentration of saturates, (ii) sulfur and (iii) viscosity-index. These properties affect the quality of our engine oil.

American Petroleum Institute (API) puts a number classifies them into five different groups.

The American Petroleum Institutes (API) classify the base stock of engine oil into 5 different groups.
The American Petroleum Institutes (API) guideline classifies the base stock of engine oil into 5 different groups.

But for us mere mortals, we don’t really need to know that.

Here’s a human-readable format.

  • Mineral oil is the most economical grade.
  • Fully-synthetic engine oil offers the best protection and performance.

Criteria #2: Additives

These are not your regular ketchup bottles! They are additives that can alters the properties of your engine oil.
These are not your regular ketchup bottles! They are additives that can alter the properties of your engine oil. Image courtesy of Arias.

We mentioned that engine oil is made from 95% base stock and 5% additives.

Just like how salt and pepper could enhance the taste of a soup, additives are chemical compounds that changes the properties of engine oil.

Additives enhances the good traits that we want, and suppresses the bad traits that we don’t want.

This makes the engine oil even better at doing what they are intended to do – to protect our engine.

Here are some of the properties that we want to control:

  • Chemical breakdown

When oxygen is present, it reacts with the surrounding.

We call this oxidation.

Over time, this will rusts our engine, degrade our base oil, and even make our engine oil acidic.

Additives like metal deactivators and antioxidant helps to slow down the oxidation process.

  • Lubricity

Remember that time when your door won’t open as smoothly as before?

I’m sure the first thing that comes to mind is to add 4D lubricants and now it can turn effortlessly.

Lubricants improves lubricity.

Which is just a fancy word for reducing harsh contact and friction between metals. With better lubricity, our car engine are more efficient.

We use friction modifiers like molybdenum disulfide to reduce friction and improve fuel economy. Anti-wear additives creates a thick film to surround and protect metal parts.

  • Contaminant Control

I have a theory.

Tiny dirt, debris and other contaminants are like secret spies for the government.

Because no matter how tightly secured your engine is, they will always find their way into the engine oil stream.

We don’t want them there but if they are already inside, we might as well keep them in check.

Additives such as dispersants are added to prevent them from forming into sludge. Anti-foam agent also helps to stop air bubble from forming.

Criteria #3: Viscosity Rating

We can tell the viscosity of engine oil by reading the label on the packaging.
We can tell the viscosity of engine oil by reading the label on the packaging. Image courtesy of Total.

Viscosity is a liquid’s resistance to flow.

When viscosity is low, the liquid is thin and flows like water. Conversely, when viscosity is high, the liquid is thick and flows like honey.

The Society of Automotive Engineers (SAE) came up with a numerical system to classify oil by their viscosity.

On every engine oil container, you’ll notice a designation like “5W-30” or “5W-40” and etc. It reads like this.

  • The “5” refers to the engine oil viscosity rating at -17.8 °C.
  • “W” is short for “Winter Grade” which suggests that it can flow better at colder temperature
  • Finally, the “30” refers to the engine oil viscosity rating at 100 °C.

That means that the numbers before and after “W” measures how much the oil thickens at cold and hot temperature respectively.

The higher the number here, the more it thickens. Conversely, the lower the number, the thinner it is.

So,

  • A car running in North Pole would benefit from 0W or 5W because it doesn’t become too thick to flow.
  • A car running in the Sahara Desert would benefit from a higher number because the oil won’t thin out too much. If it thins out too much, it can’t cushion the metal-to-metal contact.

We have 11 different viscosity grade, ranging from 0 to 60 at an increment of 5.

Criteria #4: Service Category

The American Petroleum Institute (API) service categories tell us if the engine oil is compatible with our engine technology.
The American Petroleum Institute (API) service categories tell us if the engine oil is compatible with our engine technology.

Kids love tomato soup and mushroom soup. But, they probably won’t appreciate fancy soup like Bouillabaisse – a stew of mixed herbs, fish and vegetables.

Age plays a role in our taste buds.

Cars are the same. Depending on the age of the engine, it will prefer different oil technology.

So, the American Petroleum Institute (API) came up with service categories to inform users whether the engine oil is compatible with our engine.

Service categories are named with two alphabets.

The first alphabet “S” stands for “Spark Ignition” which encompasses cars running on petrol.

The second alphabet refers to the technology of the oil. The higher the alphabet, the more recent the technology.

By referring to the image above, we can tell instantly tell if our engine oil is compatible with our car engine.

For example,

A year 2010 engine should be using API SM category oil.

A year 2015 engine should be using API SN category oil.

It is worth noting that the oil service categories are backward compatible. Which means that SN oil can be used for cars requiring API SM, SL and SJ.

As you can see, engine oil is a combination of these three factors.

Any changes in the grade of engine oil, additives, viscosity rating or service category would result in a new variation of engine oil.

Theoretically speaking, there is an infinite variation of engine oil.

But at least by now, you’ve learnt how to differentiate them from one another. That is the first step to choosing the best engine oil for your car.

Well, which engine oil is the best?

For 99% of the Malaysian out there, use fully-synthetic grade, 5W-30 or 10W-30. If you do that, everything will be A-okay.

Now, for the rare 1% that wants to drill down to the nitty gritty details…

To answer that question in short: it depends. It depends on your driving habits, the climate, and the age of your engine.

Choosing Grade of Engine Oil

This is the similar to comparing RON 95 and RON 97 petrol. It depends on what you want for your engine.

  • Mineral oil is the most economical grade.
  • Fully-synthetic engine oil offers the best protection and performance.

Choosing Additives

If you’re on the hunt for the ultimate engine oil, you’ll start to uncover a lot of aftermarket additives during your journey.

These are the “salt and pepper” that you can add into existing engine oil to alter their properties.

My advice? Stay away from the aftermarket additives.

They have their place and can improve performance. But unless you are a chemist or you have a really good idea of what you’re doing, it is generally a good idea to avoid mixing your own engine oil.

Having said that, if you are determined to formulate your own engine oil, do remember these things:

  • An inferior oil cannot become a premium product simply by adding additives. You cannot take a bad soup and make it better by adding salt and pepper. You just can’t!
  • Laboratory tests for aftermarket additives are not well regulated. They can be manipulated to “seemingly” provide great result.
  • Base oil can only dissolve a certain amount of additives. It’s like adding milo powder. Over-adding them will only leave them in powder form – like milo dinosaur at the mamak in Malaysia.

Choosing Viscosity Rating

Thicker engine oil provides better engine protection because it cushions the metal better. It becomes especially important for harsh operating condition such as mountain driving, high rpm and etc.

But at the same time, thinner oil is better for fuel economy because it flows easier. In another word, it has lesser drag and friction. Using a 5W-20 instead of a 5W-30 improves fuel economy by a whoopin’ 0.5% to 1.0%.

Choosing Service Categories

There is nothing much to choose here. Just make sure that the service category is compatible with your car model for best effect.

At the end of the day, every engine oil is a compromise and it depends on what you want from the engine. It is worth mentioning that the recommendation in the owner’s manual is a great starting point. But, it is not necessary the best option for you specifically.

Okay, how often do we need to change our engine oil?

Flushing your car's engine oil is a very important routine to keep it running well.
Flushing your car’s engine oil is a very important routine to keep it running well. Image courtesy of Robert Couse-Baker.

The magic number here is 5,000 km.

It is a good idea to change your engine oil every 5,000 km because…

Cleaner oil equals better lubricity. With cleaner oil, there are lesser friction within your engine. This improves fuel economy and lower petrol bills.

Not only that, engine oil degrades over time. Instead of being a thick layer of oil film that protects the engine, it can become sludgy (like a solid gel). This is a major contributor to internal combustion engine problems.

Engine oil can also be contaminated with tiny metal particles. Similar to our dish-washing sponge, the oil becomes dirty as it cleans your engine. These contaminants can clog up the oil filter and damage your engine.

Don't forget the oil filter! It helps to keep the contaminants away from your engine.
Don’t forget the oil filter! It helps to keep the contaminants away from your engine.

While you’re getting your engine oil serviced, you can ask your car mechanic to check if you need to change your oil filter too.

They are very cheap but can go a long way in preserving the quality of your engine oil.

Conclusion

So, that’s all you need to know about engine oil!

If you want to take better care of your car, we have written 8 Amazing Tips on How to Take Care of your Car. Give it a read! You’ll be surprised by number seven.

Enough from me, I’d like to hear from you guys.

What is your favorite engine oil for your car model and what is the price?

Leave a comment down below and we can all discuss how to make our car engine better 🙂

Until then, drive safe and drive smart!

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This Post Has 2 Comments

  1. It is a good idea to change your engine oil every 5,000 km because…

    Cleaner oil equals better lubricity. With cleaner oil, there are lesser friction within your engine. This improves fuel economy and lower petrol bills.

    You are damn right (y) Thanks for sharing 🙂 Really helpful

    Thanks again

    1. We’re glad that you find the post useful (will let the editors know!). Thank you, for taking the time to leave a comment.

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