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19/07/2021 News


As a part of regular car maintenance, oil replacement is best done as recommended by the car’s manufacturer that you can usually see in your owner’s manual.

Of the wide range of oil products available in the market, the products labelled 5W-30 and 5W-40 to indicate viscosity are commonly recommended. These products are capable to provide optimal engine protection at both low and high temperatures, which make them versatile enough to protect engines in most kinds of weather and climate.

But how do the labels differ exactly, and which one is most suitable for your four-wheeler? To find out, read more about them, their strengths, and why they are recommended by many auto manufacturers.

Understanding the label: 5W40 and 5W30

According to the multi-grading system introduced by the Society of Automotive Engineers (SAE), the “W” in the labels refer to “winter”; the first number in front indicates viscosity level in low temperature, and the last two digits indicate viscosity level in high temperature. This means the oil will work just as good at 1000 C for kinematic viscosity and at 1500 C for dynamic viscosity when the engine is running at high speed.


Having the right viscosity level is crucial – too thick, and the oil will only create more resistance on moving parts; too thin, and the oil’s protective properties will not work, causing engine parts to easily experience wear.

A 5W-30 also works better than, for instance, a 10W-30 product. To note, viscosity level may change following the changes in temperature. During the wet months and winter season, oil may become naturally more viscous.

In terms of suitability, oil products with higher viscosity level are suitable for engines of over 10 years old. These products work well to protect older engine components, although may not as effective in newer, modern engines as thicker oil will not flow quick enough. Again, to make sure you purchase the right product, always follow your manufacturer’s recommendation.

How are 5W-30 and 5W-40 different:


  • Kinematic viscosity at between 9.3 and 12.5mm2/second
  • Dynamic viscosity at 2.9mPas.


  • Kinematic viscosity at between 12.5 and 16.3mm2/second
  • Dynamic viscosity at 3.5mPas.

As the numbers suggest, the products with both labels have the same viscosity when temperature drops to around minus 300 C. At viscosity level of 5, they are suitable for the winter season and are more viscous at extremely low temperature compared to 10W-40.

However, at higher temperature, 5W-40 remains effective at over 500 C and will excel compared to 5W-30. A 5W-40 product is best for high-performing engines that work at higher temperature and operational load. For other cars, the 5W-30 is the best option.

5W-40 and 10W-40, Which One to Choose?

In short, the use of 5W-40 and 10W-40 depends on your vehicle’s mileage. The 5W-40 is more effective in vehicles with less mileage and up to 5 years old engines, while the 10W-40 is more suitable for older, high-mileage cars of 10 years and above. The 10W-40, thanks to its higher viscosity level, is effective in older engines as the components must have experience thermal expansion. A 5W-40 is thinner and may evaporate even before it can provide any protection to older engines.