Oil Number Meaning: Reading Oil Labels The Right Way

by Conner Mckay

If you own a vehicle, you most probably have seen the labels on motor oil canisters. These labels include many numbers and letters, but I’m pretty sure that most don’t properly really understand their meanings. Well, if that’s the case for you, don’t worry. You have come to the right place. In this article, we will tell you everything there is to know about the oil number meaning.

Knowing how to select the correct oil for your vehicle is really important. Putting the incorrect type of oil into the engine can reduce efficiency, worsen performance and even damage internal engine components.

Whether you change the engine oil at home or get it done by a mechanic, knowing the meaning of oil numbers can come in handy on many occasions. So, let’s get along with our discussion without waiting any longer. First, we will tell you all about what the letters “SAE” on oil labels mean.

SAE Meaning

If you are keen on learning about oil number meaning, you definitely would have come across the letters “SAE”. These three letters can be seen on many motor oil containers. However, these are not some random, symbols. They have a specific meaning that every automotive enthusiast should know about.


SAE stands for the “Society of Automotive Engineers”, which are the group that designed the viscosity coding system used in motor oils. As a result, the letters “SAE” refer to the oil viscosity specification of particular motor oils.

The Society of Automotive Engineers has a history that expands over a century. In fact, one of its original founders was none other than Henry Ford. He, along with Andrew Ricker founded the SAE as an organization for the vast number of automotive engineers working across America.

By 1916, the SAE had evolved into an organization that set industrial standards. Currently, the main role of the SAE is to ensure the consistency of products across the global markets. It oversees over 1600 practices and standards and serves several industries including the likes of aerospace, trucking, and petroleum.

The term viscosity was mentioned several times so far. You might be curious about what that is. In the next sections, we will tell you about oil viscosity in more detail.

Oil Viscosity Chart

An oil viscosity chart has a letter and some numbers that indicate the resistance of oil flow at different temperatures.

Oil Number Meaning #1 – Letter “W”

In the old days, owners had to use oil with one viscosity level during the summer and a different grade during the winter. They had to do this because the properties of motor oil changed with temperature. However, with modern technological advancements, using the same grade oil throughout the year has become a possibility.

The viscosity of motor oil is measured at both cold and high temperatures. Here, the low-temperature viscosity is aimed at simulating starting up the vehicle during a cold winter. Unsurprisingly, the letter “W” stands for Winter.

Oil Number Meaning #2 – The 1st Number

Every motor oil label comes with two different numbers. The first one, located to the left of the W indicates the low-temperature oil viscosity level. A lower number indicates oil that is thinner in viscosity. At lower temperatures, thinner oil flows faster through the engine and lubricates the components more quickly.

Oil Number Meaning #3 – The 2nd Number

The number that comes after the dash indicates the high-temperature viscosity of the particular motor oil. To put it another way, this 2nd number refers to the viscosity of the oil as it operates when the engine is warmed up to operating temperature.

This high-temperature viscosity value depends on two things. They are the engine temperature and the heat of the environment you live in.

oil number meaning

A higher number indicates a thicker oil, which is suitable for tropical areas. Thicker oil suits higher temperatures better than thinner oils, and does a good job of lubricating the internals of the engine.

We hope that this information was useful to you in understanding the oil number meaning. Be sure to use this knowledge when the time comes for the next oil change of your vehicle.

Type Of Oil

Another thing that you should pay attention to when doing an oil change is the type of oil that you put into the engine. Some of the most well-known types of motor oil include,

  • Conventional Oil
  • Full Synthetic Oil
  • Synthetic Blend Oil
  • High Mileage Oil

Let’s take a closer look at each type of oil and what they have to offer, shall we?

1. Conventional Oil

Conventional motor oil is the least expensive and most common type of motor oil out on the market. It is produced by refining crude oil. The viscosity of the oil is improved by combining it with different additives.

Although they are cost-effective, conventional oil comes with a few disadvantages. Being less refined and offering lower protection when compared to other types of oil are two of them that jump out immediately.

2. Full Synthetic Oil

Full synthetic oil is 100% man-made and does not contain any natural components. These oils are made at laboratories and adhere to the highest standards. Not only that, the manufacturing process of synthetic oils is easy to control as well.

These oils are more refined than conventional oil and offer better protection than them. Additionally, these oils have a longer lifespan, meaning that you can travel longer before needing an oil change. However, full synthetic oil is more expensive than conventional oil as well. Typically, the price difference is around $20 to $40.

3. Synthetic Blend Oil

Synthetic blend oil offers the best of both worlds as they are made using natural and synthetic materials. Overall, synthetic blend oil performs better than conventional oil and lasts longer. But, its qualities are dwarfed when compared to full-synthetic oils.

The cost of synthetic blend oil lies in the middle between conventional oil and full-synthetic. If you want a motor oil that is not much expensive but offers good performance, synthetic blend oil is the type to go for.

4. High Mileage Oil

As the name suggests, high mileage oil is designed especially for vehicles that are driven over long distances. We suggest using this type if you drive a vehicle over 75,000 miles.

High mileage oil contains a blend of different additives that prevent oil evaporation by protecting the engine seals. On top of that, high mileage oil improves engine performance as well.

Make sure to consider all these factors when deciding on what type of oil to put into your car. Other than giving your vehicle a performance boost, selecting the correct type of oil for your use case increases the reliability of the vehicle as well.

Oil Viscosity

When trying to understand oil number meaning, it is important to get to know about oil viscosity as well. In the simplest of terms, oil viscosity refers to the resistance an oil shows to flowing. In other words, the viscosity of an oil is the thinness or thickness of a certain oil at different temperature ranges.

Viscosity is one of the most important physical properties of motor oils. This property should be perfect in order to provide the best lubrication to the internals of an engine. Excessively viscous oil causes excessive energy loss from the engine.

oil number meaning

On the other hand, an oil should also have enough viscosity so that it keeps the internal engine components separated from each other.

A factor that has a great effect on viscosity is temperature. Low viscosity oils tend to pour easier during cold weather conditions. As a result, they help in getting the engine started easily during those cold winter mornings. In the same way, thicker oils with a higher viscosity perform better in warm temperatures and keep the engine running at its optimal level.

Oil Weight Chart

The oil weight number is assigned by the SAE depending on the rate at which a particular oil flows at a specific temperature level. This is done by testing the oil at different heat levels. A scale is presented by the SAE to comprehensively understand the oil grading.

Typically, heavier and thicker oils are assigned with a larger number. On the other hand, lighter and thinner oils are assigned with a lower number. Originally, these oil numbers consisted of a single digit. As time progressed, this has evolved into the two-digit numbering system we all are familiar with today.

There are a number of factors that should be considered when selecting the correct type of motor oil for your vehicle. We will discuss them with you in the next section of the article.

Oil Specifications By Vehicle

Oil specifications differ from vehicle to vehicle. So, you should pay attention to several factors when selecting the engine oil to put into your vehicle. Some of the most crucial factors that should be considered are,

  • Manufacturer Specifications
  • Engine Oil Type
  • The Driving Environment
  • Oil Viscosity Grade
  • Oil Standards

You might be confused about how these factors influence the purchase decision. So, we thought of discussing each of these factors in further detail.

1. Manufacturer Specifications

One of the first and most important things that you should pay attention to when choosing a motor oil is the owner’s manual of your vehicle. It contains all the information about what type of oil is best suited for the vehicle’s engine. New improvements done to engines with the goal of increasing efficiency and performance require new oil formulations to achieve the best results.

2. Engine Oil Type

Choosing the type of engine oil is another important decision. as the base oil makes up close to 90% of the engine’s oil composition. There are two types of base oils, namely mineral oil and synthetic oil.

Mineral oil offers sufficient lubrication while having a reasonable purchase price. However, there are some cons to using mineral oil as well.

Requiring frequent oil changes and the risk of containing impurities that lead to sludge build-up in the engine are two that immediately come to mind.

On the other hand, synthetic oils have some advantages and disadvantages as well. When compared to mineral oils, these offer greater protection to the engine. Synthetic oils also have higher thermal and chemical stability too. However, low solubility and higher cost are two of the biggest disadvantages of synthetic oils.

3. The Driving Environment

Having a piece of good knowledge of the road conditions and the general climate that you will be using the vehicle on is also important when it comes to selecting engine oil. Not only that, the driving conditions that you encounter daily also play a part in this decision as well.

4. Oil Viscosity Grade

Knowing the oil number meaning comes in handy when determining the correct oil viscosity grade for your engine. Usually, you can find this by either reading the owner’s manual or taking a look at the vehicle’s oil cap.

5. Oil Standards

Depending on the quality of the product, motor oils are awarded different oil standards. These are only offered if the oil in question meets or exceeds the requirements which are presented by the organizations.

These standards are marked as acronyms on the label of motor oil canisters. Some popular oil standards include,

So, the next time you take your vehicle for an oil change, make sure to consider all these factors before selecting your next engine oil.

Oil Type For My Car

Properly understanding oil number meaning and selecting the correct engine oil for your vehicle has several great benefits. Some of the most significant among them include,

  • Lubricating The Engine
  • Cleaning The Internals
  • Improving Performance And Fuel Economy
  • Increasing Lifespan
  • Lowering Emissions

Oil Number Meaning #1 – Lubricating The Engine

The main task of any engine oil is lubricating the internal components of the engine. As an engine runs, the thousands of parts inside it get subjected to massive temperatures. This has the effect of wearing down these parts, leading to reliability issues.

However, engine oil does a great job of absorbing and dissipating the heat, which reduces the strain on the components. Not only that, the lubrication provided by the oil helps the parts run smoother.

Oil Number Meaning #2 – Cleaning The Internals

As an engine runs, microscopic parts break off from it and tend to get accumulated inside. Additionally, engines are susceptible to carbon buildup as well. This is where engine oils come in. The oil does a great job of collecting these minute particles, stopping them from clogging the engine.

With time, the engine oil gets dirtier and dirtier due to this debris. That is why getting the oil and oil filter changed at regular intervals is important. Failing to do so reduces the efficiency of the engine and reduces its lifespan.

Oil Number Meaning #3 – Improving Performance And Fuel Economy

Engine oil does a great job of keeping the engine clean and healthy. In return, the engine runs better and gets the best fuel economy possible. Moreover, an engine with clean internals also generates the most power and achieves the best performance figures possible.

Oil Number Meaning #4 – Increasing Lifespan

Although modern engines are more versatile and intelligent than older ones, they still suffer from wear and tear. Sludge and carbon buildup inside the engine also plays a part in reducing the engine lifespan as well. However, engine oil helps to increase engine lifespan by lubricating the internals and getting rid of sludge and carbon accumulation.

Oil Number Meaning #5 – Lowering Emissions

A rough-running engine is the number one cause of harmful emissions. However, an engine with clean motor oil inside it does a great job of producing a cleaner exhaust. In addition, good engine oil can absorb pollutants produced by the engine as by-products. This lowers the pollution even further.

As you can see here, selecting the correct engine oil for your vehicle is one of the smartest decisions you can take, in terms of both performance and reliability.

Motor Oil Comparision

Motor oils with different viscosities have different qualities that are unique to them. As an example, let’s compare 10W30 oil with 5W30, and see what each has to offer.

Oil Number Meaning #1 – 10W30

With a low-temperature viscosity grade of 10 and a high-temperature grade of 30, this multi-grade engine oil is best suited for heavy-load engines. 10W30 oil is able to perform great at high temperatures for a long period of time. This oil has better sludge control, meaning that it doesn’t produce unwanted by-products at high temperatures.

Reducing wear and tear of engine components, keeping the engine cool during stop/start operations, providing rust protection, and giving smooth operations are some of the main advantages of 10W30 oil. Although it can be used in lower temperatures, 10W30 is best suited for warm weather use.

Oil Number Meaning #2 – 5W30

Compared to 10W30, this oil has a much lower viscosity rating at lower temperatures. Similar to 10W30, 5W30 also adds lubrication, reduces engine wear and tear, and also protects the engine from rust.

However, where this oil differs from the one we discussed previously is in thermal stability. In other words, the properties of 5W30 oil remain the same even if the temperature fluctuates. This makes it suitable to be used on a wide variety of engines, including gasoline engines, light-duty diesel engines as well as light-duty gas engines. In contrast to 10W30, this oil is better suited for use in cold weather conditions.

Both these oils do a great job in their ideal use cases. In short, 10W30 is the oil to go for if you own a commercial vehicle or a vehicle with a heavy load engine. On the other hand, owners of light-duty vehicles and private vehicles should go for oils like 5W30.

Mix Oil Weights

Mixing two similar oils with different viscosities won’t cause any major damage to an engine. However, this should only be done when absolutely necessary. Make sure only to mix oils of the same brand, as some companies use different additives than others, which can have an adverse effect on the engine.

Conclusion For Oil Number Meaning

oil change

Having a proper understanding of oil number meaning is important for any vehicle owner, as it helps in determining the most suitable engine oil for their specific vehicle. The oil number contains both a low-temperature viscosity grade and a high-temperature viscosity grade. You should select an oil with a viscosity grade that is suitable for your environment. Other factors like manufacturer specifications, oil standards as well as the type of oil should not be ignored.

FAQs On Oil Number Meaning

What Oil Does My Car Take

The best and fastest way to find out what type of oil to put into your car is by going through the owner’s manual. It may also contain information on what type of oil to use according to the climate of your area. Be sure to use an oil that is of the recommended viscosity levels and standards.

What Is SAE Oil

If an oil canister has the letters SAE printed on it, that means it complies with the standards set by the Society of Automotive Engineers. The SAE is the organization that implemented an oil classification system based on viscosity.

What Does SAE Stand For In Oil

SAE stands for the Society of Automotive Engineers. This organization was first established in 1905 and has its headquarters in Warrendale, Pennsylvania, United States. Some of the founding members of the SAE include Henry Ford, Andrew Riker, and John Wilkinson.

What Does Oil Do In A Car

Engine oil is essential for the functionality of a car engine. The most important job of it is to lubricate the internal components and minimize the friction between them. On top of that, engine oil also cleans the engines’ internals from sludge and carbon buildup, lowers emissions from the exhaust, increases fuel economy, and extends engine lifespan.

Is 10w 30 Thicker Than 5w 30

At higher temperatures, both 10W30 and 5W30 oils will have a similar thickness. However, at lower temperatures, the 10W30 will have a higher viscosity. As a result, 5W 30 will flow faster at lower temperatures, helping to get the engine started up faster.

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