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What’s the difference between 5W30 and 5W40 engine oil?

Oil Change

Vehicle owners will know that the correct type of engine oil for their make and model can be found in the pages of their owner’s handbook. Two of the most common recommendations are 5W30 and 5W40 synthetic engine oils. These products are an ideal option when owners need to start their engines under low temperatures. However, they are also effective when engines are running hotter which means that they can be employed in range of different operating conditions.

5W30 and 5W4o engine oil do have significant differences though, and in this article, we’ll take a close look at what sets them apart from each other. To help you understand which to use, and when, read on to discover why original equipment manufacturers (OEMs) will recommend one over another.

What do the terms 5W40 and 5W30 mean?

In both 5W30 and 5W40 engine oil grades, the ‘W’ stands for the word ‘winter’, as designed by the Society of Automotive Engineers (SAE) in its multigrading system. As for the number placed before the ‘W’, this indicates the viscosity or thickness of the oil at low temperatures. In contrast, the number after the ‘W’ denotes the viscosity of the oil at higher temperatures when the engine is running.

Oil viscosity is defined as the lubricant’s resistance to flow. An oil that is too thick can’t flow effectively through an engine’s innerworkings. However, an oil that is too thin is equally problematic, and cannot protect moving components from wear and tear properly. As temperatures fall, the viscosity of an oil increases but when temperatures rise, viscosity decreases.

When choosing a grade of engine oil for your car, you will typically face a trade-off between engine protection and performance. If an oil is more viscous when your engine is running, it can protect the engine components better, but could be too thick to safeguard engine performance efficiently. For this reason, it is crucial to consult your OEM about which grade of engine oil is correct. Engines are constructed differently, and as a result, selecting the wrong oil for a model is always a risk without a recommendation.

Understanding how 5W30 and 5W40 differ

In terms of low-shear-rate viscosity, the working viscosity of 5W40 at 100g is between 12.5 and 16.3 mm2/s. The operating viscosity 5W30 on the other hand is between 9.3 and 12.5 mm2/s at 100g. The two engine oils are both grade five when they are cold, however 5W30 becomes 30 grade and 5W40 becomes 40 grade under operating temperatures. In summer months, when temperatures are higher, 5W40 has higher viscosity levels than 5W30 engine oil, which can contribute to uninterrupted functionality of the engine.

For high-shear rate viscosity, the two oils also differ. The operating viscosity of 5W40 has a minimum parameter of 3.5 150g while the working viscosity of 5W30, should be a minimum of 2.9 at 150g. This indicates how much the engine oils can sustain in extreme loads.

5W30 engine oils has a narrower temperature range then 5W40. 5W30 is suitable for operating temperature between -25°C and 25°C, and 5W40 has a range of between -25°C and 35°C. In terms of oil flow, 5W30 has greater flow than 5W40. However, for providing higher pressure, 5W40 is superior. Out of the two engine oils, 5W30 is lighter, offering better fuel consumption. However, it is also more expensive to purchase.

Applications for 5W30 and 5W40 engine oils

5W30 engine oil can be utilised by various types of vehicles and operate effectively at a range of different operating temperatures. However, it is especially suited to working with engines in colder temperatures. More often used in engines with a higher mileage, while designed for winter use, 5W40 engine oil performs better under warmer temperatures.

As mentioned, both 5W40 and 5W30 engine oil have a winter viscosity grade of five. This means that the engine oils remain effective when working at temperatures as low as -30°C and are typically more viscous at exceptionally low temperatures in comparison to other engine oils option like 10W40 oils, for instance.

As a result, 5W40 engine oils are more likely to be deployed in higher-performance engines which must work under higher loads and temperatures than the norm. For example, vehicles that are operated in urban environments, that sit in traffic commonly or are driven at extremely high speeds, for example.

If the car you drive is not designed to be operated under high-performance conditions, or you drive at what is regarded as an eco-friendlier and more conservative pace, 5W30 oils are often a suitable choice. These engine oils are commonly better for specific engine components like oil pumps and can often clean the vehicle’s engine better. Due to their lower temperature range, they also have longer lifespans than 5W40 engine oils.

To promote engine health and strike a balance between performance and protection, always select the correct oil. As well as consulting your owner’s handbook, you can also reach out to qualified lubricant suppliers for advice.

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