10W30 Vs 15W40 Diesel Oil | In-Depth Comparison & A Comparison Chart

Diesel engines always demand oil that helps the engine run smoothly and protects the engine strongly. However, these two oils are popular among diesel engine vehicle owners because they provide the engine with one of the best performance.

So, what are the differences between 10W30 Vs 15W40 diesel oil? The main difference between these two oils is operating at different temperatures. First of all, 10W30 oil is effective in cold temperatures, while 15W40 is effective at high temperatures. Similarly, you will also get the differences in viscosity, additives, protection, cost, and so on.

However, this article helps you get core information about 10W30 and 15W40 and provides advantages and disadvantages. Overall, you will get a complete idea about these two oils so that you can easily make their difference and finally consider the best one.

10W30 Vs 15W40

What Is 10W30?

The 10W30 means the viscosity of the oil, which is rated 10W. It is a multi-grade oil used for heavy-duty diesel and gasoline engines. The thickness and viscosity make this oil suitable for low temperatures.

10W30 oil is easily worked in cold temperatures. Moreover, this oil also comes with protective elements that protect the engine and other components. For example, the engine is safe from tear, wear, and corrosion.

The oil is recommended for engines that travel at least 7500 miles. If the engine is not run at least 7500, the oil is unable to protect the engine parts.


  • Provides excellent performance in winter
  • Protects the engine from rust, tear, wear, and corrosion
  • Affordable to purchase
  • Offering higher film strength
  • Capable of heat resistance


  • It is not suitable for high-temperature

The price of this oil varies from brand to brand and country to country. You should check out the prices of your nearby shop or online shop.

What Is 15W40?

Like 10W30 oil, it is also a multi-grade oil. This oil worked for both the winter and summer seasons. The viscosity of this oil is truly effective for these two kinds of weather.

On the other hand, 15W40 oil is designed for old engines, and you will also use this oil for your new car engines without damaging problems.

Overall, this oil helps the engine to a quick start in the winter season. Similarly, it helps the engine to take enough pressure in hot temperatures.


  • It is suitable for both winter and summer seasons
  • Strongly protect the engines from rust, tear, wear, and corrosion
  • Worked for both old and new engines
  • It is a multi-grade oil
  • Easy to use and provides the engine long time running performance


  • This oil is unable to maintain viscosity in extreme operating conditions

This oil is more expensive than 10W30 oil. You can check out both online and offline markets to know an accurate price range.

How Are They Different?

10W30 and 15W40 have some core differences, which helps car owners consider the best. However, you will discover some core differences between these two oils from this section to get a clear concept.

  • Viscosity

First of all, you will find clear viscosity differences between these two oils. 10W30 oil flows 10-weight oil when the weather is extremely cold, or the temperature of the engines is very low.

Similarly, 15W40 oil viscosity flows 15 weights in cold weather conditions. However, this oil is ready to operate the engine at the highest temperature. It can protect the engine of 40-weights.

  • Protection

The elements of 10W30 are insufficient to protect the engine from tear and wear. Moreover, this oil is also unable to keep running the engine when the weather is bad enough.

On the contrary, 15W30 is thick and suitable for lower temperatures. The elements of this oil are ready to protect the engine from tear and wear. So, you will get better protection from 15W40.

  • Additives

The additives of 10W30 diesel oil are not added to very high quality. Moreover, it also comes with weaker film strength. On the other hand, 15W40 added very high-quality additives that are ready to protect the oil from undergoing oxidation.

  • Miles to Go

10W30 covered at least 75000 miles. On the other hand, 15W40 oil met or exceeded the requirements of API CJ-4. You can contact your oil company to learn more about this matter.

10W30 Vs 15W40 Diesel Oil Comparison Chart

You can check out the following comparison chart if you still need clarification to get a clear concept and get proper differences. So, let’s break down the following chart.

Name of Comparison10W3015W40
OxidationMore likelyLess likely
Extreme weather conditionsEfficientInefficient
AdditivesLow qualityHigh quality
CostInexpensiveExpensive than 10W30

Is 15W40 Better Than 10W30?

10W30 comes with thinner elements than 15W40 in the winter season. It is economical and provides long-time performance. So, if you stay in winter or cold areas, you can go for 10W30 without thinking anymore.

On the other hand, 15W40 oil is one of the best solutions for high temperatures. This oil provides a better solution for the engine to take enough pressure and helps the engine to avoid harmful things.

But 15W40 comes with better additives and viscosity than 10W30 oil. 15W40 is ready to provide high-quality additives and quality viscosity 10W30.

Can You Mix 10W30 and 15W40?

If you want to mix 10W30 and 15W40, you can do it without facing any trouble. There is no regulation or restriction to mix these two oils for the car or other vehicle engines.

But, you should keep in mind some serious points before mixing them. Check out the following list of points. If they match properly, you can easily mix these two oils.

  • First, you have to check out the user manual of the oil. If the manufacturer suggested mixing them, you could easily mix the oils.
  • Secondly, when the oils come from similar manufacturers, you can mix them.
  • Third, don’t mix the oil, which comes from different viscosity and additives.

Keep in mind these three points before mixing 10W30 oil and 15W40 oil. When these three points match properly, you can comfortably mix them without getting damaging issues.

Is 15W40 Oil only for Diesel Engines?

15W40 is mainly designed for diesel engines; users can also choose this type of oil for some gasoline engines.

This oil’s additives, viscosity, and other elements are compatible with gasoline engines. You should check out the user manual or the level of the oil to get a clear concept about this matter.

FAQs (Frequently Ask Questions)

Q: Is 10w30 Diesel Oil fully synthetic?

Answer: 10W30 diesel oil is full of synthetic oil. This oil comes with premium ingredients which are suitable for cold temperatures. It also helps the engine to start quickly in cold temperatures.

 Q: Can I use 15W40 instead of 10W30 in diesel engines?

Answer: Yes, you can use 15W40 instead of 10W30 in your diesel engines. Moreover, this oil has also protected the engine from harmful things like tear, wear, and others. But you should use 15W40 instead of 10W30 when the manufacturer permits you.

Wrapping Up!

10W30 Vs 15W40 diesel oil is a common debate because it is widely used in cold and hot temperatures. However, 15W40 is suitable for high temperatures and capable of taking enough pressure. Moreover, the viscosity, additives, and other elements provide the engine maximum protection.

On the other hand, 10W30 oil is one of the best oil for cold weather. It helps the engine quickly start and provides the vehicle owners economic benefits. So, you can also use this oil for your cold-weather vehicle diesel engine to get the best performance.

Read Also: 15w40 vs. 15w50 Engine Oil: What Are The Differences?


I am Engr. Z Eusuf Lubricant Specialist, Mechanical Engineer & has been working with engine lubricants for a long time and knows what makes them work best. I can help you find the right oil for your needs, and I have tips on how to keep your engine running at its best.