Engine Oil Grades

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Reading Your Engine Oil Grade & Understanding What it Means!

Have you too been puzzled by labels like “15W-30” or “10W-40”? Know that these are not an arbitrary mix of letters and numbers. These numbers denote engine oil grades in terms of their viscosity.

Research states that insufficient lubrication is the cause behind nearly 16.6% of engine failures! Yes, a proper engine oil is a must for the longevity and performance of your vehicle. Yet, many vehicle owners and drivers are uncertain about the specifics of engine oil grades. So, let’s dive into understanding these labels, oil grades, types, and more!

To begin with, let’s understand where these numbers and demarcations on engine oil labels come from.

The Society of Automotive Engineers (SAE)

The SAE is a global organisation that governs and regulates ratings for automotive parts. Engine oils have different ratings depending on multiple physical attributes. Buying the right grade or rated oil can often be confusing. So, it is essential to understand the terminology before getting into the engine oil grades.

Viscosity: It is a measure of a fluid’s resistance to flow. It gives information about the internal friction of a moving fluid.

Running Temperature: The maximum temperature at which the engine oil works efficiently.

SAE Ratings

There are two types of grades when it comes to engine oil.

Monograde Oil

Monograde oils are designed to perform within a limited temperature range. There are two categories:

Winter grade (e.g., SAE 5W) – formulated for cold climates, where the oil must flow easily at low temperatures.
Summer grade (e.g., SAE 30) – suitable for higher temperatures. It offers sufficient viscosity at engine operating temperature.

They are designed to function on a rather low spectrum of temperatures. Monograde oil is mainly used in transmission.

For example, SAE 5W is a low-viscosity oil. This engine oil is efficient at low temperatures. With an increase in temperature, it loses its viscosity. Hence, losing the lubricating property.

On the other hand, SAE 30 is a highly viscous oil. This oil is capable of running at temperatures of about 100° Celsius. However, this oil may not be suitable at lower temperatures.

Monograde oils are more common in older engines or specific machinery, though they’ve largely been replaced by multigrade oils for most modern applications.

Multigrade Oil:

The oils having multiple grades and a wider range of engine running temperatures are multi-grade oils. They specify the viscosity rating for both low and high temperatures.

Multigrade oils are engineered to perform across a wider temperature range. The first number (with a “W” for winter) indicates cold temperature viscosity, while the second number indicates performance at high engine temperatures. For example:

15W-30 oil stays thin enough to flow during the cold start at -15 celsius, but stays thick enough to protect the engine at high temperatures like a 30-grade oil.

This dual functionality makes multigrade oils more versatile and suitable for modern engines in varying climates.

How to Read Engine Oil Grade

To help you interpret the grades and find the best grade engine oil, here is how to read them:

Engine oil grading: Engine oil grades are the alphanumeric combination, written in the format ‘XXW-XX’. In this combination, XX represents the viscosity of the oil at the specified temperature. The first two digits indicate viscosity at low temperature, while the latter two digits state the viscosity at high temperature. The letter W represents Winter or Weight.

Engine oil grade meaning:

So in case of 5W-30 Oil

An oil with 5W will have lower viscosity, making the oil thinner at low temperatures (in comparison to 15W). This means the oil will flow easily in cold conditions and hence offer efficient lubrication during cold start.

Similarly, 30 indicates the oil’s viscosity at high engine temperatures (at 100°C or 212°F). A higher number means the oil stays thicker at high temperatures, offering better protection under heat and load.

Choosing the best grade of engine oil: The wide difference between the oil viscosities indicates better suitability for a wide range of temperatures. Furthermore, the choice must be such that the oil is neither too thin nor too thick. The thinner oil will be unable to offer protection, while the thicker oil will put an additional load on the engine.

Engine Oil Grades for Winters

The engine oil grades list of commonly used oils includes:

Engine Oil Grades List	Suited For	Property
0W-20, 0W-30, 0W-40	Areas with low temperatures normally around -35 celsius	They have zero viscosity in cold conditions, making the oils thin and easy to flow. This property makes them suitable to cold-start the engine in low temperatures. Further, they become thicker as the engine reaches its normal operating temperature
5W-30, 5W-40	Areas with a medium range of temperature, neither too low nor too high	The engine oils rated at this grade maintain viscosity across a range of temperatures, and they are generally thin at higher temperatures
10W-30, 10W-40	Areas with extreme temperature ranges	It has high viscosity at low temperatures, which further increases when the engine reaches normal operating temperature.

Other Engine Oil Grades

Besides SAE, there are additional oil gradings to know about. It includes:

API Service Classification: The American Petroleum Institute (API) is a USA-based grading system. The labelling categorises the oil as either diesel or petrol.
The label ‘S’ indicates ‘Spark Ignition’ and hence is an indicator of a petrol engine.
The other label is ‘C’, which means ‘Compression Ignition’ and indicates a diesel engine.
These symbols can be followed by another letter, where the higher one indicates advancement of the oil.
ILSAC Rating: The International Lubricants Standardization and Approval Committee (ILSAC) ratings offer more insights into the engine oil’s performance and efficiency standards. The ratings follow the notation- ILSAC GF-x, where “x” is a number that shows the version of the standard.

Each new version means the oil meets newer and stricter rules for things like saving fuel, protecting the engine, reducing harmful deposits, working better with modern engines
So, the higher the number, the more up-to-date and better performing the oil is.

OEM Approvals: The Original Equipment Manufacturer (OEM) approval indicates certification from the specific manufacturer, confirming that the oil is suitable for vehicles of their brand.

Conclusion

Engine oils and lubricants are an integral part of the automotive industry. Having the right knowledge about what oils do and which lubricant may be right for your vehicle is as essential as buying the right vehicle. Using the best grade engine oil and lubricants for a particular vehicle will guarantee a smooth-running engine and increase the longevity of the vehicle substantially.