5w30 vs 5w40 oil: What is the difference?

Changing your car oil regularly is crucial for providing the proper lubrication to the engine. Oils have a rating according to their viscosity and how they perform at extreme temperatures, such as 5w20, 15w40, etc. In this article, I am going to provide an insight into the differences in 5w30 vs 5w40 oil, which will help you choose the oil that can withstand the highest temperature in your area and still flow in cold weather. 

5w30 and 5w40 are motor oil abbreviations that few people understand. We’ll understand why it’s crucial to know their meaning and why you can’t pick any bottle of engine oil and hope for the best. 

What Is 5w30 Oil?

5w30 is an SAE (Society of Automotive Engineers) classification of viscosity class. This classification gives 5w30 the flow characteristics of oil at a specific temperature. To this end, engine oil has different viscosities according to the temperature. 

When it’s cold, oil is thick and hard to flow, and it becomes thin and easy to pour in hot weather. Engine oil should protect the engine in that it can run in winter without giving the engine problems with cold starts. 

Similarly, it should maintain its capability of lubricating the engine when running at average and high temperatures. 

The 5 in 5w30 indicates the viscosity of the engine in cold temperatures while the 30 indicates its thickness at high temperatures of 212 degrees Fahrenheit. “w” stands for winter. So, 5w means the viscosity of the oil in winter.

A low number before W means the oil will flow better in cold temperatures than oil with a high number before W. For example, 10w30 is thicker than 5w30, and it will be harder to flow in winter than 5w30. 

Where to Use 5w30

5w30 has operating temperatures between -13°F to 77°F. Thus, it is ideal if you live in an area with high seasonal temperature fluctuations. Also, it is more favorable in cold climates since it will flow easily compared to oils with a rating of 10w or 15w. Hence, you won’t have cold start problems since it protects the engine’s components in extreme temperatures. 

Similarly, 5w30 engine oil is suitable for long drives where the oil is subjected to a wide range of operating temperatures. The substance is versatile and referred to as full-range engine oil. 

Main Features of 5w30

  • Great engine lubrication
  • Improves overall motor performance 
  • Offers excellent engine wear protection 
  • Ideal for normal to extreme driving conditions 
  • Suitable for gasoline, diesel, and multi-valve fuel engines

What is 5w40?

Engine oil has to accomplish its purpose within a range of temperatures. The “w” in 5w40 indicates the season, which is winter, according to the Society of Automotive Engineers (SAE). 

The number before w shows the oil’s viscosity at low temperatures, and that’s 5 in this case. On the other hand, the 40 indicates its thickness properties at high operating temperatures of up to 212°F.  

5w40 is a multi-grade oil. That’s why it has two numbers compared to single and mono-grade oils that have only one number. 5w40 has thin base oil additives that allow it to operate like a mono-grade oil in cold temperatures. Yet, it will not lose its viscosity entirely when it heats up.

5w40 optimizes the health of your engine by protecting it from deposit and sludge buildup. It also ensures that the engine revs at low temperatures and the oil circulates efficiently when temperatures dip below zero. 

Therefore, 5w40 gets the engine parts moving fast like single-grade motor oil in winter, but it will not become thinner than a single-grade oil rated at 40. 

5w40 engine oil is recommended for gas-powered engines in European vehicles and American pickup trucks with diesel engines. 

Main Features of 5w40 

  • Reduces oil utilization 
  • It has a viscosity grade of 5 
  • Resists thinning incredibly well
  • Suitable for vehicles that use leaded and unleaded gasoline

Difference Between 5w30 and 5w40 

5w30 Vs. 5w40 Comparison Chart 

Viscosity 9.3 to 12.5 mm2/s 12.5 to 16.3 mm2/s
Temperature Range -13°F to 77°F-13°F to 95°F
Oil Flow Flows smoothly Less flow
Thickness LighterDenser
Mileage More fuel-economical Less fuel-economical 
Application Gas and diesel multi-valve engines Leaded and unleaded gasoline engines
Thinning Resistance Low High 
Oil Utilization Average Low 

These key differences between 5w30 and 5w40 will help you understand which oil is best for your vehicle. 


The first difference in these oils is their ability to flow. 5w30 working viscosity ranges from 9.3 mm2/s to 12.5 mm2/s. On the other hand, 5w40 operates between 12.5 mm2/s and 16.5 mm2/s. 

These numbers indicate that 5w30 flows faster than 5w40 since it is less viscous than 5w40. Due to its higher flow rate, it provides better lubrication and protection to engine parts. When using 5w30, your engine gets the characteristic humming sound associated with a new motor.

5w30 Vs. 5w40 Hot Weather Performance 

5w40 has higher viscosity at operating temperatures. In hot weather, the oil weights for summer with a high density like 5w40 are better since it contributes to uninterrupted engine functioning. 

Fuel Economy

5w30 and 5w40 oils work differently. In this regard, the 5w30 is considered more economical since it works with various engines thanks to its viscosity. It flows better into the multiple parts of the motor. Therefore, it is economical because not much of it is consumed. Yet, 5w30 has better mileage regarding fuel economy because of its performance. 

Extreme Driving Conditions 

Again, 5w30 is better than 5w40 in extreme driving conditions. As such, it is suitable for gasoline and diesel multi-valve engines. Nevertheless, 5w40 is ideal for leaded and unleaded gasoline engines due to its low volatility. 

Because of 5w40’s viscosity, it reduces its utilization in these engine’s combustion chambers. Plus, it has excellent resistance against heat, providing thermal protection for combustion engines. 


Can I use 5w40 instead of 5w30?

Yes. You can use 5w40 instead of 5w30, but it all depends on your preference. Since 5w40 is more viscous at high temperatures, it is better when outdoor conditions reach above 95°F. 

What is viscosity?

The viscosity of engine oil refers to how easily it flows at a specific temperature. Thick oils have a honey-like consistency and are more challenging to flow than thin oils with a water-like consistency. 

With this in mind, thin oil flows better in winter, making it easier for the engine to start and lubricate various engine parts. Meanwhile, thick oil is better at high temperatures since it will not lose lubrication qualities. 

Main Takeaways 

Changing your oil is one of the most critical stages of regular maintenance. And choosing the right oil weight is quite challenging for people, especially DIY-ers. Now, you have a good understanding of the differences between 5w30 and 5w40. I hope this article makes your engine oil choice more straightforward since, as you can see, the 5w30 has different performance qualities than the 5w40.