0W20 vs 5W20

0W20 vs 5W20 – The Best Engine Oil For Your Car

Welcome back to another article, where we will be comparing the difference between 0W20 vs 5W20.

These two engine oils are more commonly seen in newer cars with smaller engines. They are often turbocharged, also.

If it’s a topic you aren’t familiar with, looking at all these numbers and variants can appear quite daunting. Don’t worry though, we will go through it step-by-step.

In this article, we will explore…

To jump straight to the section where we compare 0W20 vs 5W20, click the second bullet point above.

You may have seen one of our other articles comparing different engine oil types. If you are looking for one of them, please check out the following:

That being said, let’s delve into it.

0W20 vs 5W20 – What Do The Numbers Mean?

As we have just mentioned, it might be somewhat intimidating to look at all the different types of engine oil and become disheartened. There are so many!

In this section, we will explain what all the numbers mean. What does the “0” mean? What about the “W” or the “20”?

Keep on reading to find out.

Numbers: A Measure Of Viscosity

The numbers you see in the “name” of the oil (called its “grade”, which is what we will call it from here on in) refer to how viscous the oil is.

In simple terms, viscosity is the “thickness” of a liquid. The thicker a liquid is, the more viscous it can be said to be.

In terms of physics and chemistry, there’s actually a lot more going on, but this definition is enough for now.

The numbers on the grade of oil represent how thick the oil is. For example, let’s compare the first numbers in the oils we are comparing today – 0W20 vs 5W20.

You can see that the second number is the same on both – “20”.

The first number, however, is different – “0”, compared to “5”. (Technically, these numbers are attached to the “W” too, but we’ll come onto that in a little bit).

Since 0 is less than 5 (if you know your math), it means that (at a certain temperature) 0W20 is less viscous than 5W20. Or, if you prefer, it’s thinner. This is all relevant to temperature, though, as we will explain shortly.

What is Viscosity?

Encyclopedia Britannica defines “viscosity” as follows:

Resistance of a fluid (liquid or gas) to a change in shape, or movement of neighbouring portions relative to one another. Viscosity denotes opposition to flow

Check out the full page here.

While we can think of viscosity as simply being about how thick a liquid is, in technical terms, it’s about how much internal friction a liquid has. How much it stops itself from flowing.

This might be a difficult concept to grasp, so it might help to use an example.

Picture what would happen if you were to fill one measuring jug with water and another with honey, before tipping them at the same rate and time. The water would flow out quickly and relatively smoothly, whereas the honey would slowly gloop towards the spout.

In terms of viscosity, we would say that honey is more viscous than water.

The more viscous a liquid is, the more friction it produces as it flows. This friction is a force that is opposed to the direction we want the liquid to be going, and therefore it’s a force that needs to be overcome. The greater the friction, the more energy has to go into pushing the liquid round.

This is still the case for engine oil.

The more viscous the oil, the greater the amount of energy needed to push it around the engine. It also means that more energy can be thought of as wasted.

Engines with high-viscosity oils are usually (not always, it depends on a huge variety of factors) less efficient than those with low-viscosity oils.

Viscosity is also affected by temperature – the greater the temperature, the lower the viscosity.

What Does the “W” Mean For Engine Oil?

As we touched on just now, the viscosity of a liquid depends on its temperature. As liquids become hotter, they get less viscous.

This can present problems for an engine. On cold mornings, the car has to do more work to pump the thicker oil around the engine. As the engine warms up, it needs a greater amount of lubrication, and so a thin oil might not protect the parts enough.

Because of this, oils are written as multigrade oils. This means that they have more than one grade.

Most oils have two grades. These are written in the following format:

  1. Number + W
  2. Number

The “W” stands for “winter”. It shows that this is the oil’s grade in cold temperatures.

Technically, we should write 0W20 like 0W-20. This clearly shows the difference between the two grades and is how you’ll usually find it written on the products you buy.

The first number refers to tests done at about 0 degrees C, which simulates winter conditions. The number represents its viscosity at this temperature.

The second number is all about how viscous the oil is when the engine is at operating temperature. These tests are done with the oil at 100 degrees C.

The two numbers are slightly relative to each other, but only marginally. For example, for 0W20, the oil behaves like an SAE 0 oil at 0 degrees C and like an SAE 20 oil at 100 degrees C. They are related, but there is a huge difference due to the temperature change.

Why Do We Use Multigrade Oils?

Up until the 1960s, most cars had to have two oil changes per year. One would happen in summer, the other in winter.

We use multigrade oils to avoid having to do this.

These two oil changes per year often had to be done due to cold weather protection. The main aspect of this is starting the car. Less stress is put on the battery when starting in the cold. This is because the oil can be modified to be less viscous in the cold than it would be naturally, meaning the oil pump has less work to do to force it through the engine.

Not everywhere in the world uses multigrade oils. If you live somewhere with a relatively consistently warm climate, such as California, you might find that your car runs on a monograde oil. One of the most common monograde oils is SAE 30.

Read about it in more detail here on machinerylubrication.com.

What Are The Main Benefits of Multigrade Oils?

When compared to monograde oils, multigrade oils are almost universally better. Almost.

As we said, if you live in a warm, consistent, dry climate that very rarely dips below freezing, there isn’t much need for multigrade oil.

However, for the rest of the world, there is.

Here are some of the main benefits of using multigrade oil.

  • The car will be easier to start when it’s a low temperature outside, such as in winter. There is less strain put on the battery.
  • It eliminates the need for changing the oil twice a year – the one oil lasts all year round.
  • Additives in the oil can make for better high-temperature performance, as well as better starting conditions.
  • The oil is effective over a wider temperature range.
  • Fuel economy is generally better.

For the majority of us, therefore, using a multigrade oil is a bit of a no-brainer.

However, it’s not always the case. There are also a couple of disadvantages to multigrade oils:

  • Due to all the additives put into them, they cost more than standard monograde oils.
  • The viscosity modifiers can occasionally be sheared – “broken”, to most of us. This would lead to the oil being irreparably damaged and losing its viscosity, meaning that your engine would wear more.

What Viscosity Modifiers Are Used In Multigrade Engine Oils?

Viscosity modifiers – also known as Viscosity Index improvers or VI improvers – are polymeric molecules that respond to temperature. When it’s colder, the chain is contracted and it does not affect viscosity. When it gets warmer, the chain relaxes and stretches, which increases viscosity.

It might help to think of it a little bit like a slinky. When it’s cold, the viscosity modifiers act like a slinky when it’s all squashed up and not in use. As the temperature increases, the polymer acts similarly to when you stretch out the slinky.

The bigger the polymers become, the more they will get in each other’s ways, to use simple imagery. This means that the internal friction of the liquid that they’re in will increase. As we looked at earlier, this is how the internal viscosity becomes higher than it would naturally be.

Note that the basic rule of physics is the same – as temperature increases, viscosity decreases. The use of viscosity modifiers doesn’t change this. It can, however, decrease the rate at which viscosity drops off.

This brief article on machinelubrication.com explains it nicely.

We have put together a basic graph to show you how SAE 10, SAE 20, and 10W20 might compare on axes of temperature and viscosity. Please note that this graph is not an accurate representation of how the oils behave under temperature, but just for illustrative purposes.

engine oil 10w20 vs sae 10 sae 20

Note: For illustration purposes only.

How Are SAE Grades Assigned?

The multigrade ratings that you see on engine oil products – 0W20, for example – come about from strict testing processes.

To get its multigrade, an oil is measured in four tests. Two of these are done at low temperatures (freezing) and the others at higher temperatures, which represent the operating temperatures of engines. This is done at 100 degrees Celcius – water’s boiling point.

The results of the first two tests give the oil its first grade – the cold one – the one followed by a “W”. The results of the second test give it its other number.

Again, Machine Lubrication has an excellent article covering all this.

How Do 0W20 vs 5W20 Compare?

Having looked at all that, then, we come to the main focus of our article. How do 0W20 vs 5W20 compare to each other?

Thinking about everything we have looked at so far, we can see the difference between the two.

Here is another graph – the same one as shown earlier – but this time including how 15W20 would show on this graph.

10w20 vs 15w20 compared graph

Note: For illustration purposes only.

In “winter” conditions, 15W20 is slightly thicker than 10W20. As the temperature increases to 100 degrees, we see that the viscosity is now the same.

The same principle would apply when comparing 0W20 vs 15W20.

The reason this happens is due to the different kinds of – and amounts of – additives in the oils.

This means that, when comparing 0W20 vs 5W20, 0W20 would be marginally less viscous – thinner – on cold mornings. In theory, this makes the car easier to start when the temperature is low. In reality, though, it’s not as simple…

0W20 vs 5W20 – Does That Mean I Should Use 0W20, Even If My Owner’s Manual Says To Use 5W20?


Definitely don’t do that.

There are many articles you might find online which will tell you that “one oil is better than the other” – for whatever reason.

In truth, you can’t think of it that way.

Think of it this way – your car has been specifically designed to run on the oil that the manufacturers recommend. Everything has been designed so that it will flow nicely, run well, and, most importantly, be efficient. Efficiency is the name of the game when it comes to the modern automotive market.

Cars are also designed and modified for the target geographical markets. A car sold in Northern Canada will be slightly different from its equivalent brother sold in California, for example.

Always. Follow. The. Owner’s. Manual.

This should be the only source of authority for what you put in your car. It’s what mechanics will follow, too, although perhaps an online database version instead.

0W20 vs 5W20 – Which Is Best?

It’s not really the right question.

The better question would be (rather boringly), “which oil does my owner’s manual tell me to put in?”. Whatever it says, use that one.

Only in exceptional circumstances would it be advisable to put the wrong kind of oil in your car – perhaps if you had to top it up in an emergency and had no other kind available. Even then, you should run the car as slowly as possible and make your way to the nearest auto shop immediately. It would be more advisable to simply call a recovery service out, though.

If you’re playing around with a project car, then okay. That’s completely up to you. And, you never know, if you’ve installed some new components (or removed some old ones), a different engine oil might give an increase in performance and efficiency. Or it might do some serious damage over time.

For the vast majority of us, who use cars on the road and don’t want the constant hassle of them breaking down, don’t deviate from the owner’s manual. Things can only get worse.

So, as we compare 0W20 vs 5W20, there’s no reason to think either one is “better” than the other, for some reason. Both have different properties which produce marginally different results.

Whatever engine oil your car has been designed for is the best one for your car. End of.

How To Change Your Engine Oil

Sometimes, all you have to do is top up your oil. Check out this video from the AA on their website.

Changing your engine oil is one of the simplest jobs to do on your car. It’s also one of the most important.

0w20 vs 5w20 engine oil between metal
Engine oil functions as a lubricant between metal surfaces.

The main purpose of engine oil is to function as a lubricant. It keeps the hot, moving, metal parts away from each other by forming a sort of barrier between the two surfaces.

As well as this, it also:

  • cleans sludge out of the engine.
  • neutralizes acids that form in the engine.
  • cools the engine – it is a sort of secondary system to the coolant system.
  • protects the engine against rust.

These functions are achieved using additives to the oil.

You can read more about how engine oil works here on Wikipedia.

Neglecting to change your oil could lead to serious problems. In short, any of the above functions may stop working probably. You could have a sludge buildup (which is both an awful problem and disgusting at the same time). The engine could begin to rust. It could also begin to overheat easily.

All of these could potentially lead to a catastrophic failure and a complete engine rebuild or swap. That means money – money that could have been saved with a quick oil change.

For most new cars – or to keep your car’s service history up to date – you’ll have to get it serviced reasonably regularly. This is effective for keeping your warranty valid and making the car easier to sell when it comes to it.

If you’re in this position, it makes sense to just take your car to an authorized dealer. They will stamp your service booklet and that’s that.

If you have to change the oil yourself in between services for some reason, you could do it yourself, although if you aren’t too sure of yourself, it’s probably best to get some help. Better to be safe than sorry.

Engine Oil Change – You Will Need

  • The new oil (never reuse old oil) – with the correct grade and quantity, both of which you will find in your owner’s manual.
  • A funnel, for pouring the new oil in.
  • Rags and parts cleaner, for cleaning up.
  • PPE – gloves, especially, and potentially goggles for when you are underneath the car. Long sleeves are also recommended – coveralls if you have them.
  • An oil pan, for catching the waste oil.
  • A wrench or ratchet, for removing the sump plug.
  • A torque wrench, for replacing the sump plug.
  • Granules, in case of any spills.
  • An automotive ramp (tested and safe) OR a level surface (with 4 axle stands and a trolley jack if your car is too low to get underneath – make sure these are tested and safe too, as you will be working underneath the car).
0w20 vs 5w20 why car must be level engine oil
If the car isn’t level, some of the oil in the sump won’t drain out properly.

Engine Oil Change – Steps

  1. First of all, get the car in position on the ramp or the flat ground. If it’s too low, jack the car up at all 4 corners and put axle stands in. Always make sure you’re safe. If you aren’t sure, it’s best to stop now and have a rethink. The car must be flat so that all the oil and sludge drains out. Make sure you aren’t anywhere near any drains – it’s illegal to let oil into the water system.
  2. Open the hood and open the oil cap on the top of the engine. This allows the air to flow through, helping the oil to drain out.
  3. Get in position underneath the car and place the oil pan so it will catch the oil as soon as it pours out. Be careful. The angle might catch you out (I’m speaking from experience). Use the ratchet or spanner (or Allan key) to remove the sump plug, watching out for the oil pressure pushing the plug out before you’re ready.
  4. Allow the oil to drain. Get out from underneath the car for safety reasons but don’t take your eyes off the oil pan. As the oil pressure decreases, the flow rate will decrease. You could end up with a puddle on the floor if you leave it too long. Again, I’m talking from a very messy experience.
  5. It will probably take about 10 minutes for the oil to drain out. Once there’s only a very occasional drip, you can replace the sump plug and take the oil pan out from under the car. Legally dispose of the oil – this will probably involve calling someone out to your house. Use the torque wrench to tighten the sump plug up to its recommended value. You can find this in the owner’s manual or sometimes engraved on the sump itself.
  6. Clean up underneath the car if necessary.
  7. Pop the new oil in using the funnel. Make sure it’s the right grade and that you put the right amount in!
  8. Replace the oil cap.
  9. Start the engine. It will sound awful for a few seconds. This is because there is no oil in the system – the pump is pushing it around. The noise should stop after no more than 10 or 15 seconds. If it persists, switch the engine off immediately and check everything. You might need professional help.
  10. Check the oil level with the dipstick. If it’s between the maximum and minimum levels indicated, you’re all good to go!

Check out this video from Scotty Kilmer on changing your oil.

0W20 vs 5W20 – Concluding Off

Overall, when we compare 0W20 vs 5W20, it’s interesting… but not particularly practically relevant.

You should always, always, always use the manufacturer’s recommended oil for your car.

We hope this article has been useful!

Related Content

Approved Tools

These tools have been tried and tested by our team, they are ideal for fixing your car at home.

Leave a Reply

Your email address will not be published.