5w30 vs. 5w40 Oil Guide: The Major Difference Between 5w30 And 5w40

When the time comes to change the engine oil, some car owners needing an oil change may go to the mechanical shop. They view that they should know which oil is suitable for their vehicle. Others don't consider the manufacturer's manual to be the final say when choosing the right oil for their car. 

It is worth mentioning that choosing car oil should strictly be your responsibility. Therefore, when you have to choose between 5w30 vs. 5w40, you need to know which oil is best for the engine, as it will ensure the engine's optimal performance.

What's The Purpose Of Engine's Oil?

Engine oil is the lifeblood of your engine. It reduces friction between all those parts, which means less wear & tear on them over time - that's why you should change it regularly! The energy from burning fuel escapes through combustion as well but luckily there are ways around this by using timing belts or camshafts instead so they don't need constant vigilant maintenance themselves (though annual servicing will be needed).

With oil in between, pistons ring and cylinder walls to reduce wear; provide better compression which keeps contaminants out while improving fuel efficiency. If there were no motor oils then cars would never move because their components are constantly being sparked together producing heat until they finally break down due to lack of lubrication  This process creates noise but not necessarily power!

But even if you have poured oil into the engine - you should not relax before time. You need to keep an eye on it all the time. The first thing to keep an eye on is the amount of oil. If there is not enough oil in the engine, it will not be enough to lubricate all components, and as a result, the parts will overheat. As a result - you get overheating, pistons burnout, melting of valves, and as a result - an extremely expensive repair! The second thing to watch out for is the condition of the oil. It gets dirty during operation - this is a normal and natural process. But it needs to be changed periodically. If this process is ignored, dirt and metal particles in the oil will work as an abrasive, destroying and damaging the engine from the inside!

Why is the viscosity of your engine oil is so important?

Viscosity refers to a fluid’s resistance to flow. The higher the viscosity, the more slowly it flows. 

If your engine is not designed to use some specific sort of oil, for example, 5W-30, then you will experience poor performance and wear. Your car was built with a specific type of motor oil in mind - one that has the right viscosity at both 40°C (104 ° F) AND 100 ° C or 212 º Fahrenheit! That’s why today's standard recommendation by most experts across industries including automotive repair professionals such as myself: Use 30 weight oils when engines are running hot; 10 weights if they're cold.

Oil thickens when it’s cold (its viscosity increases). Alternatively, it thins when it’s hot (its viscosity decreases).

If you use an Oil that thins too much in cold weather, it won’t circulate through every part of this machine as readily leading to wear on moving parts and potentially dangerous situations where things are not separated properly due to lack of lubrication.

How To Read Engine Oil Names?

The Society of Automotive Engineers (SAE) has created a numerical code for grading motor oils according to their viscosity characteristics. Multigrade oils were developed in order to provide protection across multiple temperature ranges. SAE viscosity index includes the following numbers: 0, 5, 10, 15, 20, 25, 30, 40, 50 and 60. As a thumb rule, lower the number means lower viscosity and vis-a-vis.

What is 5w30?

5w30 is an oil having a lower viscosity, as the letter 'W' represents winter, whereas its number represents oil viscosity at high temperatures. As the oil viscosity changes with the temperature, a multi-graded oil can protect the range of temperature.

In 5w30, the number 5 represents the oil's viscosity at cold temperature. If the number is lower, the oil will certainly be thinner and flow smoothly in the engine, even at cold temperatures. 

Number 30 represents how fine the oil works at average operating temperatures. This oil is also known as multi-graded oil, as it can be used in any condition. Mainly it is used in the light-duty petrol and the diesel engine, and the viscosity ranges from 5 to 30.

What is 5w40?

This motor oil helps make the engine work smoothly, as well as its moving parts from overheating because of friction. 5w40 transfers the heat by the combustion cycle, and in return, it keeps the engine clean by burning the by-product and protecting the engine from oxidation. The engine’s internal and external temperatures can affect how the motor oil performs.

The lower viscosity of 5w40 is 5, and the higher is 40, which means that it can be used in a vehicle having leaded and unleaded gasoline. This oil is less viscous in cold temperatures, whereas it is viscous at high temperatures because of the higher viscosity grade of 40. This engine oil is used by gas-powered engines and diesel pickup trucks.

Difference between 5w30 and 5w40

  • Both have different viscosities when it is about 5w30 vs. 5w40 motor oils.

  • 5w30 is capable of working smoothly on the engine because of its thickness. On the other hand, when it is about 5w30, it is not that thick.

  • 5w30 can work smoothly in low as well as high temperatures. 5w40 can work smoothly only in cold temperatures.

  • 5w30 engine oil is more expensive than 5w40, and it may not be readily available everywhere. In comparison, 5w40 can be found anywhere.


When we talk about 5w30 vs. 5w40, there is quite a bit of difference between these oils. The viscosity of both the oils is different, and they perform well in the ideal conditions. However, it depends on your vehicle's engine and how the oil will work. 

5w30 is more expensive as it functions smoothly in the engine’s internal part, and it can also be beneficial in the future. Therefore, 5w30 is a lot better than 5w40 in performance.