Can I Use 10W40 Instead of 5W30? (Answer Explained)

With various grades, there are so many different options available in engine oils. Choosing the right engine oil weight becomes difficult as there are plenty of confusing choices. Today, there are some industry-grasping multi-grade engine oils produced like 10W40, 5W30 or 20W50.

These engine oils are made with so much testing in the lab. Some are included with additives, lubricants and adhesives. But, unfortunately, we can not see or measure these chemical components with our bare eyes.

What we can only experience is the difference in the performance. Today we have taken 10W40 and 5W30 to describe the performance of each oil. Although both of the oil have nearby numbers mentioned, they still have differences.

So, without further ado, let’s get into the details.

Can I Use 10W40 Instead of 5W30?

Well, if you put 10W40 instead of 5W30, your car engine will face a different problem. Finally, faulty functions will reduce your car’s overall performance. Now, let’s figure out why you shouldn’t do this .

What will happen if I put 10W40 instead of 5w30?

Being a thicker oil 10W40 can harm your engine if your engine requires a thinner oil. Although a bit of interchange in engine oils can be good, it is highly recommended not to use one to replace another.

5W30 is specially designed for cold temperatures. It is a thinner type of oil that allows running the oil inside at a cold temperature where oil jamming is a significant concern. So, if you put a thicker oil like 10W40, your engine would not work appropriately. Besides, the oil will get clogged and lose its efficiency to work. 

Moreover, the oil would get thicker and could not reach all the components when you start the engine. As a result, there will be a lack of fast lubrication and engine wear and friction. 

So, you see. Using 10W40 instead of 5W30 can cause your engine a lot of hazards. 

Can I Mix 10W40 and 5W30?

Mixing different oil weights can cause damage to your engine sometimes. So it is not recommended to do so. But you can mix nearly identical multi-grade oils in some cases. 

As 5W30 is a thin oil, mixing it with 10W40 will give you a much thinner oil. Eventually, it will increase its operational capability in cold weather. But, it will not be good enough in hot weather.

Further, the oil will become less viscose and would not lubricate the engine components appropriately. Thus, it will increase friction and wear.

So, be careful mixing between two different grade oils. Even if you mix them in between,  it would be best to stick to the same brand for both oils.

Comparison Chart (10W40 vs. 5W30):

High viscosity oilLow viscosity oil
Thicker type of oilThinner type of oil
Best for hot temperature areaBest for cold temperature area
Suitable for older model car enginesSuitable for newer model car engine
Not suitable for often sat down enginesSuitable for often sat down engines
SAE certifiedSAE certified
Lubricates wellLubricates well

In-depth Discussion – 10W40 vs. 5W30:

There are four types of engine oil. They are – Conventional, Semi-Synthetic, Synthetic and Racing oils. These different kinds of oil are used for other purposes, but they have the grades and grading system. 

So, whichever type of oil you use, it is vital to understand the grades first. 

What Does 10W40 and 5W30 Means?

The 10W40 oil and the 5w30 are so close yet so different engine oils. They react and perform differently. Let’s elaborate on their performance.

What does 10W40 mean?

If we separate the two parts of the grade 10W40, we will notice the first difference. Here, we can see a number before the letter “W” and a number after the letter.

The first number, 10, tells us the cold temperature tolerance power of this oil. The last number, 40, tells us the hot temperature tolerance power of this oil. Considering this much knowledge, we can say, 10W40 is good to go to oil.

What does 5W30 mean?

Separating the two parts of 5W30 engine oil, we can also see two different numbers. One before the letter “W” and one after the letter too. 

The first number, 5, tells us how efficiently the oil works nicely in cold temperatures. The last number tells us the capacity of this oil to function appropriately in hot temperatures.

Which One Is Higher In Viscosity – 10W40 vs. 5w30?

Although, most people’s viscosity considers only the thickness of the oil. But in actuality, it finds the thinness as well. 

The viscosity of an oil is determined considering both of the numbers in the grade. As the first portion of the grade number describes thinness, we can see, 5W30 is thinner than 10W40. Here, the lower the number, the thinner the oil.

On the other hand, the second portion of the grade number describes the thickness of the oil. So, we can see, 10W40 is thicker than 5W30. Here, the higher the number, the thicker the oil is.

After getting through the thinness and thickness of both oils, we can conclude that 10W40 is higher in viscosity than 5W30. 

Which One Gives High mileage – 10W40 or 5W30? 

Thicker and high viscous oils give more mileage as we have already got to know that 10W40 is a thicker oil. We can say this one will provide higher mileage than 5W30.

However, the 5W30 is not bad in mileage either. It works excellent and provides the best mileage in colder temperatures. 

Which one to choose – 10W40 vs. 5W30?

The answer is, choose the one that your user manual says. This is the best option that could ever be for your engine. If you are not finding the exact one only then, you can consider switching between engine oils.

We have come across and know that 10W40 is suitable for hotter weather. So, if you are driving your car at a hotter temperature, this thick oil is an excellent option for you.

Besides, we knew that 5W40 is suitable for colder weather. So, if you are driving your car in a colder place, this thin oil is the best choice for you. If you do not drive often and your engine sits idly for a time, 5W30 will also work great here. This oil also prevents oil from getting frozen and lumped up by sitting.


Does 10W40 hurt a 5w30 engine?

Yes. 10W40 engine oil will hurt 5W30 engines. Because 10W40 is way thicker than 5W30. You are not supposed to use different-purpose oil in your engine.

Which is better, 5w30 vs 10W40?

Both 5W30 and 10W40 are suitable for engines. Where 5w30 is the best low viscosity oil for colder areas, 10W40 is the best high viscosity oil for hotter regions.

Can you go from 10W40 to 5w30?

No. It would be best if you do not go for 10W40 to 5W30. This will make your engine lose lubricity and increase engine wear and friction.

How long does 5W30 oil last?

Either it is a 5W30 or any other oil, you should go for an oil change as per the user manual requirement. When you change the oil filter, change the oil as well. For assumption, you can use 5W30 for 7,000 to 8,000 miles. Do not run more than this. 

When should I use 10W40 oil?

You should use 10W40 if your owner manual says that you need a high viscosity thick oil. Or, to drive at a hot temperature, you can use 10W40 as your ideal engine oil.

Final Words

The primary purpose of engine oil is to protect your engine. Be careful; you do not destroy it by experimenting and switching to different oil. Again, it is not suggested to switch in between other viscosity oils.

Whichever oil you choose from above, it is strictly advised to understand the owner’s manual engine oil recommendations. Always try to stick with single multi-graded engine oil. It will increase your engine’s work capacity, HP, RPM and many more.

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