5w40 vs 15w40: Difference and Comparison

Engine oils are among the most critical factors in ensuring an engine runs smoothly.

However, since there are so many different types of oil, motorists are sometimes misled, and they wind up using an oil that isn’t ideal for their engine, which can cause significant difficulties in the long term.

Key Takeaways

  1. 5W40 is more suitable for cold weather than 15W40 due to its lower viscosity.
  2. 15W40 is more appropriate for older engines with high mileage and wear than 5W40.
  3. The numerical values in both designations indicate the oil’s viscosity at low and high temperatures.

5w40 vs 15w40

5W40 has a lower viscosity rating, making it better suited for colder climates up to 5 degrees. 15W40 is better suited for warmer climates up to 15 degrees.5W40 has a lower viscosity rating than 15W40, which means it flows easily at low temperatures, making it a better choice for a colder climate.

5w40 vs 15w40

5w40 is a multigrade oil that may be used in any season, as indicated by the letter “W” in its composition, and has a more extensive application range than 15w40.

The oil’s protective properties may be maintained between -30 °C (-22 °F) and +40 °C (104 °F), as indicated by the “5” parameter, and +40 °C (104 °F), as noted in the “40” parameter.

Oil viscosity in 15w40 classes is mainly determined by expected ambient temperatures, especially the beginning temperatures.

The oils in question are classified using the conventional categorization system due to the letter “W” in their names (SAE). Both oils are multigrade and may be used in both summer and winter.

Comparison Table

Parameters of Comparison5w4015w40
AdvantageDue to good cleaning from impurities, almost no deposits occur on the engine.It can be used everywhere.
Temperature range-30 °C or -22 °F and +40 °C or 104 °F-20 °C or -4 °F and +40 °C or 104 °F
Range of useWideNarrow
Engine specificityEngines with more than 6000 milesCan be used everywhere.
Preferred climate conditionColdWarmer

What is 5w40?

As it is a multigrade oil, 5w40 could be used in every season, as indicated by the letter “W” in its formulation, and has a broader range of applications than 15w40.

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The oil may keep its protective characteristics between -30 °C (-22 °F) as well as +40 °C (104 °F), as shown by the “5” parameter, and +40 °C (104 °F), as indicated by the “40” parameter.

Almost no deposits form on the engine due to thorough impurity removal. Protects the engine from wear by retaining its protective characteristics for a more extended period.

It performs better in colder environments than 15w40, especially starting the engine; it has strong heat resistance so that it can handle aggressive driving styles and harsh situations.

This 5w40 engine oil should be changed every 15000 km and 9000 miles. 5W40 oil is better than most for cars with similar annual mileage because it is an all-season oil with a wide operating temperature range.

It is more costly than 15w40. It’s suitable for engines that aren’t too worn out. Several engine manufacturers are opposed to using 5w40 in their vehicles.


What is 15w40?

Oil viscosity classes are primarily advised based on projected ambient temperatures, particularly the starting temperatures.

Because of the letter “W” in their names, the oils in question are categorized using the standard classification (SAE). They are both multigrade oils that can be used in summer and winter.

As a result, the parameters 15, W, and 40 have the following meanings according to SAE standards:

The low-temperature viscosity with which this oil type maintains its benefits is indicated by the number 15. Cold resistance for the 15w40 is roughly -20 °C or -4 °F; number 40 is the polar opposite.

According to the product description, 15W40 will maintain its protective characteristics up to +40 °C (104 °F); the letter W denotes all-season use, which implies the lubricant can be used in both cold and warm settings.

This type of oil is ideal for automobiles with worn engines because it preserves them better, avoids corrosive activities, and encourages the clearance of sludge.

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With such a high degree of wear, it provides more economical fuel usage in internal combustion engines. The oil is less expensive to produce; it is suitable for engines in hotter climates.

If you’ve had a more vigorous driving style and are operating under challenging conditions, the viscosity will be lost.

Because 15w40 oil loses its properties below -20 ° C or -4 degrees Fahrenheit, it is not ideal for cold temperatures. Some manufacturers advise against using oil in their engines.

Replacement intervals of less than 5000 kilometres (3000 miles) are recommended.


Main Differences Between 5w40 and 15w40

  1. Temperatures between -20 °C or -4 °F and +40 °C or 104 °F are good for 15w40, whereas temperatures between -30 °C or -22 °F and +40 °C or 104 °F are suitable for 5w40.
  2. 15w40 is preferable in hotter areas, while 5w40 is preferable in colder climates.
  3. In addition, because 15w40 protects the engine better than 5w40, it is commonly used in engines with more exceeding 60.000 miles.
  4. 5w40 has a wider range of vehicals to be used with as compared to 15w40.
  5. 5w40 has a property of cleaning which leads to no deposition on engine whereas the advatange of 15w40 is it suits the car whose engines got worn out due to continuous use.
Difference Between 5w40 and 15w40
  1. https://www.koreascience.or.kr/article/JAKO200818259611390.page
  2. https://www.sciencedirect.com/science/article/abs/pii/S0301679X11002106

Last Updated : 06 July, 2023

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6 thoughts on “5w40 vs 15w40: Difference and Comparison”

  1. The article offers a detailed breakdown of the differences between 5w40 and 15w40, making it easy to choose the best engine oil for my car.

  2. The author’s argument about the cost of 5w40 engine oil is not convincing. Cost should not be a deciding factor when it comes to protecting an engine.

  3. I disagree with the author’s views on the replacement intervals of the 5w40 oil. Research has shown that it can last longer than suggested here.

  4. I found the explanation of 5w40 and 15w40 oils to be very clear. It has helped me understand which type of oil is most suitable for my engine.


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