Engine Oil Grades: Understanding the Different Types - CARS24

Engine Oil Grades: Understanding the Different Types

Engine Oil Grades

Picture this: you’re at the garage, about to get an oil change. The mechanic asks you what grade of engine oil you’d like, and suddenly, you’re teleported back to high school, trying to choose between Science, Commerce, and Humanities. The choices can seem overwhelming. In this blog post, we’ll look at the different engine oil grades and their related vocabulary to help you make an informed decision. 

As the name suggests, engine oil is an essential component of a vehicle’s engine, performing key functions to ensure smooth and efficient operation. Think of engine oil as the vital fluid of your car – it keeps the engine clean, cool, lubricated, and efficient. 

What does engine oil grade mean?

Engine oil grade refers to the level of quality and performance of engine oil based on industry standards and specifications. These standards determine the viscosity, or thickness, of the oil and its ability to flow at different temperatures, as well as the level of supplements added to provide protection, cleanliness, and durability to the engine. In simple terms, the different grades are a way to measure the ability of engine oil to perform the crucial functions of lubricating, cooling, and cleaning the engine.

Also Read : From Fuel to Function: Working of the Car Engine Explained

How to read engine oil grade?

How to read engine oil grade?

Reading an engine oil grade is easier than you think! Most engine oils are marked with a two-part identification and classification system consisting of two numbers separated by a hyphen. The first number is the oil’s viscosity rating at lower temperatures, usually expressed in the SAE (Society of Automotive Engineers) scale, and the second indicates the oil’s viscosity at higher temperatures.

For example, an engine oil marked “15W-40” would have a viscosity rating of 15 at low temperatures and 40 at high temperatures, making it suitable for use in a wider range of temperatures. A “0W” rating means that the oil is specifically formulated for use in cold weather, while a higher second number, such as “50”, indicates that the oil is thicker and better suited for high-performance engines.

But there’s more to the story. It’s important to note that not all engine oils follow the SAE identification and classification system, and some may also have additional designations, such as “synthetic” or “energy conserving”, to indicate the type of base oil and additives used. So, when choosing an engine oil, always consult your mechanic or the vehicle’s owner manual to find the recommended grade and specifications, and make sure to read the label carefully to ensure you’re getting the right oil for your car. Remember, the wrong engine oil is just as harmful as no engine oil!

Also Read : 10 Engine Maintenance Tips

When it comes to engine oil, the different grades determine your vehicle’s smooth and efficient functioning. Here’s a closer look at a few of the commonly used engine oil grades around the world:


This type of engine oil is thin when the engine is first started. The “0W” refers to the viscosity of the oil when the engine is cold, which is 0. When the engine reaches normal operating temperature, the viscosity of the oil becomes 20


This engine oil is designed to perform like a 0-weight oil at start-up and a 30-weight oil when the engine reaches normal operating temperature


This engine oil is engineered to function as a 0-weight oil when the engine is cold and a 40-weight oil when the engine reaches normal operating temperature


This is the most commonly available and widely used engine oil in India, and many Indian car manufacturers recommend it


This is a fully synthetic engine oil that behaves like a 5-weight oil during cold start and a 40-weight oil at normal engine operating temperature


This engine oil provides a 10-weight performance at cold start and a 40-weight performance when the engine reaches normal operating temperature

Also Read : How to Choose Best Engine Oil For Car?

Types of Engine Oil Grades

Types of Engine Oil Grades

The right engine oil depends on the type of engine and driving conditions. Engine oil grades can be divided into several categories based on viscosity, performance level, and the type of base oil and additives used. Some of the most common types are:

1. Conventional or Mineral Oils

These are the most basic and widely used engine oils, made from crude oil that has been refined and blended with additives for improved performance. They are labelled with an SAE viscosity rating such as “10W-30” or “20W-50”

2. Synthetic Oils

Synthetic oils are human-made oils created from a concoction of different chemical compounds and offer improved performance compared to conventional oils. They provide better protection and efficiency at higher temperatures and often have a wider operating temperature range. Synthetic oils are usually labelled with the letters “SYNTH” or “SYN”, followed by their viscosity rating

3. High Mileage Oils

High-mileage oils are designed for engines with higher mileage and provide extra protection and cleaning to older engines. They are typically labelled with “High Mileage” or “HM” on the label

4. Energy Conserving Oils

These oils are designed to improve fuel efficiency and reduce emissions. They are often labelled with the “Energy Conserving” or “EC” designation and have a lower friction coefficient compared to conventional oils. These oils are less harmful to the environment and are a good step towards a sustainable future

5. Diesel Engine Oils

Diesel engines require oils with higher viscosity and different additives to handle the high compression ratios and increased soot levels found in diesel engines. They are usually labelled with “CJ-4” or “CI-4+” to indicate their suitability for diesel engines

Terminology on engine oil labels

Engine oil labels contain different numbers, symbols, and abbreviations, and can often be confusing. But it’s not difficult once you familiarise yourself with the different terminologies. Here are some of the most common terms you need to know about:

1. SAE Viscosity Rating

SAE rating indicates the oil’s viscosity at different temperatures. For example, a label that reads “10W-40” means the oil has a viscosity of 10 at low temperatures (W stands for winter) and 40 at high temperatures

2. API Service Classification

API classification indicates the oil’s performance level and suitability for use in petrol and diesel engines. The API symbol features a rain cloud design with SM or CF in the centre that identifies the oil’s performance level

3. ILSAC (International Lubricant Standardization and Approval Committee) Rating

ILSAC is a joint effort between the API and the Japanese Automobile Standards Organization (JASO) to develop standardised performance and fuel efficiency criteria for engine oils. The ILSAC rating is indicated by the words “ILSAC GF-x” on the label, where “x” represents the performance level

4. OEM (Original Equipment Manufacturer) Approvals

OEM indicates that the vehicle manufacturer has approved the oil for use in their engines. For example, a label that reads “Mercedes-Benz Approved” means that the oil has been tested and approved for use in Mercedes-Benz engines

5. API (American Petroleum Institute) Resource Conserving

API index indicates that the oil is designed to improve fuel efficiency and reduce emissions

6. Synthetic Base Oil

This indicates that the oil is made from synthetic or human-made base stocks. Synthetic oils offer improved performance and protection compared to conventional oils. The word “Synthetic” or “Syn” is usually displayed on the label

Also Read : How To Check Engine Oil level Of Your Car Correctly

7. Engine Oil Grades Chart

It is important to note that while engine oil grade charts can be a helpful reference, it is always best to consult your trusted mechanic or the owner’s manual of your vehicle and the oil label for the recommended specifications and approvals.


Q. How do I know when to change the engine oil?

Regular oil changes are recommended based on the manufacturer’s specifications and your driving habits, typically every 12000 to 15000 kilometres or 6 to 12 months.

Q. How to select the right grade engine oil for my car?

It’s recommended that you consult your trusted mechanic or the vehicle’s owner’s manual for the recommended oil viscosity and performance specifications. Check for API service classification, ILSAC rating, and OEM approvals.

Q. What does 20W-40 mean in engine oil?

The “20W-40″ labelling refers to the oil’s viscosity, or thickness, at different temperatures where”W” stands for winter and “20” indicates the oil’s viscosity at low temperatures, while “40” indicates its viscosity at high temperatures.