Skip to content

There are many factors that should be taken into consideration when you want to choose the engine oil for your vehicle. Choosing the right one can be tricky, that’s why you need to take a few steps in order to get there. First you need to know your car manufacturer and series, then you need to know the conditions you face while driving, that’s why you should know your driving environment. You also should have an idea about the types of engine oil and most importantly when comparing them you should know that each type has a different viscosity grade, which is what this article mainly talks about.

What is Engine oil Viscosity?

Engine oil viscosity is a measurement of oil’s weight and actually describes how thick the oil is. Normally, oil tends to thicken, or increase in viscosity, at low temperatures and thin out, or decrease in viscosity, at higher temperatures. However, motor oil thickens as it heats up and thins as it cools down. This is counter to regular oil and tends to be the most confusing aspect of understanding motor oil viscosities. Manufacturers usually put special additives in the oil to make it thicken when heated. The thickened oil clings to your engine’s internal parts, increasing the lubrication provided by the oil.

Why is engine oil viscosity so important?

The most important thing to consider when choosing an engine oil is viscosity, or oil thickness and flow. The viscosity of the engine oil used in your vehicle can affect many aspects such as fuel economy, engine cleanliness and overall vehicle performance. Selecting the right oil is important for every car owner, as using an engine oil with the right viscosity for the driver's driving habits and the external environment can help reduce fuel consumption and extend the life of the vehicle. Oil coats the moving engine parts so that they don’t grind against each other and wear down.

A. How to read and measure engine oil viscosity?

When choosing the engine oil you need for your car, the most important thing to keep in mind is the engine oil viscosity rating. Look for the viscosity grade recommended by the manufacturer, which you can find in your owner's manual. The best oil is an oil that provides thick support for your engine when it’s running hot, but won’t turn into a water-like liquid when it gets cold. Engine oil viscosity, or thickness, is given by a code on the can. This code describes how thick the oil is, and what sort of engines it is meant to lubricate. You need first to look at the can and find this code, in TOTAL products you can find it written on the front of the can, it’s a number that is divided into two parts and looks like: (10W-30). The first number in the code is the starting viscosity. This rates the thickness of the oil when the engine is first started. And the letter W stands for the word (winter). 10W oil has an oil viscosity rating of 10 at winter temperatures. The second number is the high-temperature viscosity. When this oil is heated by the engine, it has a viscosity rating of 30. You also need to check your owner's manual of your car to make sure that you are using oil of the correct viscosity rating.


B. Which is better: High or low engine oil viscosity?

Engine oil viscosity is critical to keep metal parts separated within the engine and the proper viscosity grade does that. The grade of oil you should use depends on engine clearances, operating conditions, and the climate. Take into consideration where you live. If you live in a cold climate, you probably want to use oil with an SAE 0W-20, 5W-20, or 5W-30 viscosity for instance. These are examples of lower engine oil viscosity.

However, what if you live in a warm climate and you want an oil that offers more high-temperature protection?

In that case, an SAE 10W-30, 10W-40, 15W-50, or 20W-50 would be more suitable. These four are examples of higher engine oil viscosity. Thin oils have lower viscosity and pour more easily at low temperatures than thicker oils that have a higher viscosity. Thin oils reduce friction in engines and help engines start quickly during cold weather. Thick oils are better at maintaining film strength and oil pressure at high temperatures and loads.



Can I use thicker oil in my engine?

It's best to use the recommended engine oil viscosity, but people usually wonder if using oil of higher viscosity grade than usual can harm their engine or not. While it’s best to use what’s recommended as TOTAL provides the right tools to help, inadvertently using a viscosity one grade higher or lower than what’s recommended generally poses no long-term harm. In fact, some automakers allow switching to a lower viscosity oil depending on the weather and the engine condition.