Can I Use 10w40 Instead Of 5w30?


Engine oil provides the necessary lubrication for moving parts of an engine. The oil acts as a lubricant that allows the engine components to move around each other without creating excessive wear.

But the question is – can I use 10w40 instead of 5w30? The answer is – NOT RECOMMENDED. To understand the whole concept in detail, please read the post till last.

The first step to consider is to consult the manual. There is a list of the recommended oil weight based on the temperature in your car owner’s manual. Whether it is standard engine oil viscosity 5w30 vs 10w40, or other. You will need to choose an oil with the recommended weight from a brand that displays a starburst symbol confirming that it has been API tested.

XWYY – What do these specific numbers mean?

These numbers represent the viscosity of the engine oil. Whenever you are going to add engine oil to your car, check your recommended oil viscosity specific for your car.

The first number(s) proceeding the alphabet “W” represents the viscosity of that engine oil at a colder temperature. It indicates the engine oil’s viscosity relevant to the engine’s temperature at the ignition (starting) point. The lesser this number, the easier for the engine to start at the colder temperature, which means the engine oil with a lesser number has more tendency against freezing at the colder temperature.

“W” stands for winter. Not for the weight as ambiguous by many people.

The numbers after the “W” indicate the viscosity of the engine oil at the higher temperature while the engine is running. The higher the number here, the higher the tendency found in the engine oil against thinning due to higher temperature and maintain its viscosity well to lubricate the engine components.

See Also: How Often To Change Engine Oil

Difference between 10w40 and 5w30

When we talk about 5w30 vs 10w40, their viscosities’ main difference is at lower and higher temperatures.

The viscosity of 5w30 will be 5 at a lower temperature, i.e., when the engine is going to start. While the viscosity of 10w40 will be 10 at the same lower temperature.

The phenomenon is – the lower the viscosity here, the easier and good for the engine to start due to the low viscosity of motor oil. It prevents the engine to wear and tear. Because at the start the temperature of the engine is low and the oil with low viscosity here performs better and reaches all over the engine components due to its more thinning ability (lower viscosity). So that’s why 5w30 performs better than 10w40 at the starting point.

The lesser the temperature in your area (colder weather), the lesser the oil viscosity will be recommended for the engine. But remember these viscosities are not the actual viscosities of motor oil as mentioned. These are just standard numbers at 100 degrees Celsius.

Now talking about the numbers present after “W” in 10w40 vs 5w30. It indicates the viscosity of the oil when the engine is heated up and the temperature of the oil comes to its maximum temperature during operation.

Thus here, the viscosity of 10w40 oil would be 40 at high temperature, while the viscosity of 5w30 will be 30. The phenomenon is – the higher the number here, the better the oil maintains its viscosity, and its ability to resist thinning out (maintain its thickness) is more due to high temperature.

Hence 10w40 oil performs better in the high temperature than 5w30 and maintains its optimum thickness to avoid engine wear and tear.

5w30 vs 10w40 – Which one is best to used?

Generally, the best engine oil viscosity to use is one that is recommended in your owner’s manual according to your area whether.

You will need to choose an oil with the recommended weight from the best brand that displays a starburst symbol confirming that it has been API tested.

If you get confused between both of these oil that 10w40 performs better in high temperatures, while 5w30 performs better in low temperatures, then which one is best? Don’t worry, don’t be confused about it.

Remember, the composition of your engine is always suitable for a specific oil having specific viscosity grades. The internal temperature of your engine will shuffle in between the range of that recommended specific viscosity. That’s why you just need to choose the oil recommended in your owner’s manual according to your local prevailing temperature.


Can I use 10w40 instead of 5w30?

Each engine is designed with specific tight tolerances seals in the engine, therefore mechanics always recommend specific viscosity grades engine oil as per its manufacturing.

If the recommended oil in your car’s manual is 5w30. It better always use 5w30 oil. The components and seals of the engine are designed according to a specific thickness and viscosity for the lubrication. If you use more thick or viscous oil like 10w40, your engine oil will not flow properly all over the components, especially in those tight lubrication points.

See Also: What Are The Primary Functions Of Motor Oil?

Why do we need to use recommended engine oil?

Every car’s engine is built in a specific way and requires a specific viscosity, that’s why the manufacturers recommend that specific oil viscosity with the main reason.

If you decided to use the heavier viscosity oil than recommended, the engine would not be able to use it, nor it reaches out at the particular places where it is needed. Ultimately the engine would be dragged down and causes wearing in the internal parts.

In this case, the oil pump creates lots of pressure, which causes the engine oil to be bypassed and not use for proper lubrication.

On the other hand, if you use low viscosity oil, it will not create much-needed pressure in the engine to pump it to the places where it is needed to be reached.

In both cases, the situation is not good for the engine and causes wear and tear of the engine. You might not be able to note it at the start, but it will ruin the longevity of your engine. That’s why it is always advised to use the recommended engine oil as per the owner’s manual based on the temperature.


Generally, modern engines do much better with lighter oil.

If your car has an older high mileage engine or an old model car, generally it has a thicker oil recommendation like 10w40. But in modern engines, the recommended oil viscosity is generally 5w30, 5w20, 0w20. The oil with these viscosity grades is light viscous and performs well due to tight lubrication points found in a modern engine.

If any different grade oil has to be used due to any compulsion, we would recommend you lighter-weight oil instead of heavier ones.

Weather Condition also matters a lot.

Generally, it also depends on weather conditions. If you’re in a warmer temperature, using 10w40 instead of 5w30 could not be harmful. But it’s not an ideal situation.

Although using havier and more viscous oil than recommended in a colder temperature like in Central NY in February would cause a problem.

See Also: How To Check Engine Oil Quality – A Complete Guide

Using 10w40 instead of 5w30 also not good for the startup of the engine.

Using 10w40 in place of 5w30 is also not good for the startup of the engine especially in cold temperature, and your engine could cause damage due to low lubrication and cause more wear and tear to the engine.

With 10w40, when it gets warmed up then its flow is thicker than 5w30, which causes loss of little gas. Mileage and lubrication are also not as good, plus it puts more strain on the oil pump.

Never go thicker than a 5w30 and that especially in an older higher mileage engine in warmer climates.

Using 10W40 instead of recommended 5W30 would invalidate your engine warranty.

In a 5W30 engine, you can use 0W20 oil in cold climates and that would be good for many companies like Ford. They won’t say it’s good, but they’ll still honor the guarantee.

But 10W30 stretches, they would probably consider this an error, and if the oil was not directly causing the failure, they would comply with the warranty.

But the 10W40 is a long way off, and I bet they wouldn’t be so happy with an engine problem if they found the 10W40 on a bad engine.

Dealers often purchase cheap oil in bulk.

Your service station agent could compel you or advised you to use 10w40 or any other than recommended and satisfy you regarding your worries. Never follow him and refused to do so.

Many service stations purchase a bulk quantity oil type at a cheap price, that’s why they only have that single kind of oil at their service station. They always recommend that single kind of oil to all of their clients, by neglecting the specifically recommended oil for each engine.


Again we will advise you always use recommended engine oil according to your owner’s manual. Using 10w40 instead of 5w30 is not a good decision. The 5w30 is very common, and ideal for both lower and higher temperatures in the engine, and is recommended by most manufacturers.

However, if you have any problem regarding engine leaks and wear, instead of using 10w40, it is better to consult a good mechanic. These problems could be caused by many other factors, that can be well diagnosed by a good mechanic and get rid of it.

See Also: Switching To Synthetic Oil After 100k Miles


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