6.0 powerstroke 5w40 vs 15w40

6.0 Powerstroke 5w40 Vs 15w40 – Which One should You Use?

If you own a vehicle with a 6.0 Powerstroke diesel engine, the type of oil you use is very important since it must be high-quality and efficient. By the end of this article, you will be exposed to which oils you should use and why you should use them. Through the discussion of “6.0 Powerstroke 5w40 vs 15w40”, a detailed understanding of the two types of oil, 5w40 and 15w40, is obtained.

Stay till the end of this article to learn how to choose the best oil to keep your 6.0 Powerstroke diesel engine running efficiently for a long time.

What Is 5w40?

We must first clarify two significant things in this discussion. Let’s first see what 5w40 means. Simply put, this is a common viscosity grade for diesel engine oil. The “W” here stands for winter. And the number prior to “W” implies the viscosity at which the oil operates at low temperatures. In contrast, density at higher temperatures is indicated by the number after “W.”. You should definitely know essential facts about this oil before purchasing it.

Accordingly, 5w40 performs well at low temperatures. The engine does not need to warm up better. Due to its low viscosity, the oil flows well throughout the engine, even at low temperatures. It greatly affects the efficiency of the engine.

What Is 15w40?

Simply put, this oil is also a type of oil used for diesel engines with suitable viscosity even for low-temperature situations. “W” stands for winter again. The first digit gives information about the viscosity at the average engine temperature, and the last digit provides information about the viscosity of the oil at generally good temperatures. This is a good choice for engines with a 6.0 Powerstroke used for good towing in severe weather conditions. It also provides excellent protection for your diesel engine. 

Can You Use 5w40 instead of 15w40?

Of course, you can use that! Let’s analyze it in detail.

The technical issue here is straightforward to understand. Before this section, we talked about these types of oils, where some understanding of the oil’s viscosity may have been gained. Viscosity is the ability of an oil to flow at a constant temperature.

Here we talked that 5w40 is a thin oil enough to flow throughout the engine even at the lowest temperature. And you know that the first and last numbers show the nature of oil flow at a specified temperature. For example, suppose you take the viscosity range of both 5w40 and 15w40. In that case, the viscosity range of 15w40 also includes the viscosity range of 5w40. Therefore, 5w40 oil can be used even for an engine with 15w40. However, suppose there is recommended oil specified by your vehicle manufacturer. In that case, it is better not to neglect those instructions.

6.0 Powerstroke 5w40 Vs 15w40

This is a bit of an even comparison. Both these oils are very similar to each other. However, there are slight differences. Let’s try to understand the difference here using some important points. Then, you can identify what type of oil is right for your 6.0 Powerstroke engine.

  • Viscosity:The main difference between 5w40 and 15w40 oils is the viscosity of these oils. The numbers given here are viscosity ratings. Usually, only one number is used in engine oil rating. For example, take “SAE 40”. But in both types of oil we are talking about, two numbers are mentioned. It implies that viscosity range in an environment with varying temperatures.

5w40 oil is less dense than 15w40 when operating at much lower temperatures. But finally, at a constant temperature, both viscosities equal each other. That is the idea implied by the last two digits.

  • Fuel Economy: Fuel economy is something that anyone who owns a vehicle usually focuses on. Angel oil is one of the main factors affecting this. The viscosity of the oil affects fuel efficiency. The reason is that the oil is thinner, so the fuel can be pumped better.

Now you might think that 5w40 is ahead in terms of fuel economy. But that is not true. Here 5w40 creates thinness in a low-temperature environment. But at normal engine operating temperature, there is no difference between these two.

  • Durability:Experts say that engine oils with high viscosity are more durable. But there is a difference in viscosity between these two oils only in a cold environment. Since the viscosity is the same at normal temperatures, there cannot be much difference in durability between the two.

Above, we discussed the main differences between 5w40 and 15w40. But there, we don’t see enough significant differences to recognize.

Is 5w40 Thicker than 15w40?

There is an obvious answer to this. 5w40 oil is no thicker than 15w40 oil. Here you can get a clear answer from the first digit itself. As we discussed earlier, the digit prior to “W” implies the viscosity value. Higher values indicate that it is thickest than the lower values. Therefore, you may understand that 15w40 is more viscous.

Is 5w40 Better for Hot Weather?

You may have gotten some understanding of this from the previous sections. But the answer is simple. Not only 5w40, but both can be used equally at higher temperatures.

Look at the top of the viscosity range to understand the answer clearly. Simply put, refer to the value after the letter “W.” You can see both as 40. That means both have the same viscosity at higher temperatures. That is, both oils flow evenly in the engine at high temperatures. So the answer is that there is no difference between the two.

Will 5w40 Increase Oil Pressure?

Usually, the oil pressure will be increased, if you use oil that comes with more viscosity or more thickness. But compared to 15w40, 5w40 can be considered less dense. Simply put, 5w40 oil cannot increase the oil pressure. This is because this thinner oil does not create much resistance as it passes through the engine.

If you think a little deeper, this can only happen in a cold environment. In an environment where the temperature is relatively high, the viscosity of 5w40 is the same as 15w40. In such a case, there is a possibility of increasing some oil pressure.


Regarding the 6.0 Powerstroke 5w40 vs. 15w40, we have clarified many issues. According to our conclusions, although there are fewer differences between these two, it can be said that 5w40 is better for starting your vehicle in a cold environment. In addition, a comprehensive and detailed discussion about these two types of oil was also successfully completed. This article will undoubtedly add a lot of knowledge to oil selection for the longevity of your 6.0 Powerstroke engine.

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