Engine Oil Grades Explained: Know Your Car Engine Oil

The performance of your car is severely impacted by the engine oil that it uses. In this article we will explain what are the different oil grades denoted on those oil cans.

Engine oil arguably plays the most critical role in maintaining the health of your car’s engine. If an inappropriate oil is selected for a vehicle, it can have severe and long lasting impacts on the life of the engine. So, it becomes imperative to choose the right lubricant engine oil for our vehicles for smooth running and best efficiency.

There are high chances that you may not be well versed with the various engine oil grades that are mentioned on engine oil cans. In this snippet we will try to explain just that in simple plain speak. But, before that, let us have a brief of what engine oils are and what do they do. Here we go!

What Are Engine Oils?

In simple terms, engine oil is a lubricant that acts as a layer between the different moving components of an engine. It helps in preventing the wear and tear of the engine parts, by reducing friction between them.

Engine oils also help in cleaning the sludge from the engine, which would otherwise result in blockages. More importantly, engine oils typically have anti-corrosion properties that prevent the different parts of the engine, including the cylinder blocks, from corrosion.

While this makes us understand the importance of engine oils, the question is – how do you determine which is the right engine oil for your car? It is quite tricky because engine oils have different grades that are meant to be used in different conditions and vehicles.

Let us talk about engine oil grades then…

What Are Engine Oil Grades?

Engine oils have different grades based on the viscosity they possess. If you do not understand viscosity, it is the property of fluids that describe how easily the fluid flows. For engine oils, viscosity can be defined as its resistance to flow. Typically, smaller the viscosity value, thinner is the oil and vice versa.

Engine oils grades are denoted by two numbers, for example, ‘5W-30’. The first number ends with the letter ‘W’, which stands for Winter. This number denotes how the oil flows when it is cold, say – during the time of engine start-up.

The second number signifies the flow of oil when it is hot, at normal engine working temperatures. Usually, smaller the number, better will it flow. However, while thinner oils flow easily, they may offer lesser prevention against friction between moving parts. So, it is extremely important that you use the right grade of engine oil in your car. Here we explain.

More on Engine Oil Grades

Consider the example of oil grade ‘Xw-Y.’

As mentioned above, the number ‘X’ describes how the oil flows when it is cold. The oil must not be very thick at colder temperatures (during engine start-up), and it should flow smoothly. Hence, lower the value of X, better is the oil for cold starts.

On the other hand, the number ‘Y’ denotes how easily the oil flows when at higher temperatures (when the engine is running). As a basic property of liquids – they become thinner at higher temperatures. Engine oils also behave the same way and may become ineffective in preventing friction.

Hence, the oil must have the right viscosity value and should flow easily at the same time. Hence, in broader terms, the higher the value of ‘Y,’ better is the oil at higher temperatures.

But different engines are designed differently. All vehicles have dissimilar requirements. Hence, it is suggested that you have a look at the owners’ manual that came with your car, to understand the oil grade prescribed for it. Otherwise, you can also contact the authorized service center of your manufacturer to know more about it.


In this story we learnt what are grades of engine oils and what are those numbers printed on the can for. Apart from the internal temperature, engine oils behave differently with the change in the atmospheric conditions. So, always ensure you stick to the manufacturers recommended grade of engine oil.

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