5W-40 vs 0W-40: Which Is Better And Why?

It is impossible to think about how an engine runs without first understanding the role and importance of engine oil. An automobile engine is comprised of several components moving, bumping, and grinding against one another.

The functionality of an engine in a car is incomplete without the lubrication of its various components. With engine oil being the only engine lubricant, they are indispensable.

Engine oil comes in different types. In this article, I will examine and compare these two synthetic engine oils: 0W-40 and 5W-40. Synthetic engine oils are compatible with heavy and light-duty engines and are suitable for winter conditions. The engine oils are both efficient lubricants. Nonetheless, a comparison using various criteria will be made.

0W-40 vs. 5W-40: What’s The Difference?

Before establishing the differences between 0W-40 and 5W-40, it is important to first explain what they are. 0W-40 and 5W-40 are multi-grade viscosity oils, exhibiting different viscosities with a change in temperature. The viscosity helps in providing protection to engines in different extreme temperatures, such as cold and hot.

0W-40 has two different viscosities depending on the temperature; 0W and 40. This means that it is 0W in cold temperatures and 40 in hot temperatures. Similarly, 5W-40 has two different viscosities, 5W and 40. It is 5W when the temperature is cold and 40 at a warmer temperature.

One of the most obvious differences is the different names of the engine oils. The ”W” in the products’ names stands for “winter,” buttressing their suitability for winter conditions. However, one of the key differences between 0W-40 and 5W-40 is that the latter is more suited for hotter weather conditions than cold weather.

Driving car in a hot weather.

The engine oils might be both suited for low-temperature conditions, but 0W-40 remains the best option for harsh temperatures because of its low-temperature viscous level of 0, compared to 5W-40. The working viscosity of the engine oils also varies. 0W-40 has a working viscosity of 3.8 to 16.3 mm2/s. The working viscosity of 5W-40 is 12.5 to 16. mm2/s.

The oil thickness between the two engine oils is consistent, evident in the figure after “W”, which is 40. Hence, the oil thickness at operating temperatures is the same across the two synthetic engine oils. Nonetheless, there are still some other differences between the two engine oils. 5W-40 can potentially pump the engine to -35 C while 0W-40 can pump engines up to -40 C.

0W-40 vs. 5W-40 Viscosity

The viscosity of the engine oil is an important criterion when making a choice. Viscosity in oil means the semi-fluid state of being thick or sticky and is used to describe it as thin or thick. Furthermore, the temperature is considered when determining the viscosity of 0W-40 and 5W-40.

The viscosity level of both oils can be explained by the first and last numbers after “W”. The first number represents the engine oil viscosity at low temperatures, and the last number identifies the thickness of the oil at operating temperatures. The viscosity scale was developed by the Society of Automotive Engineers (SAE) for engine oil.

The viscosity level of 0W-40 and 5W-40 is different and their difference is evident in their oil flow at low temperatures. In cold temperatures, low oil viscosity means the oil will thin and easily flow through the engine in harsh winter conditions. 0W-40 has a 0 viscosity at low surrounding temperatures, which means the oil thickens less and flows better in cold temperatures.

On the other hand, 5W-40 has a 5 viscosity compared to 0W-40’s 0 viscosity, which means it thickens more and doesn’t flow as much as 0W-40 under cold temperatures. This gives 0W-40 the edge in cold conditions and is the best engine oil option in such situations. It remains thin and flows seamlessly in cold temperatures and is not prone to thickening during cold situations.

The last number after “W” defines the 0W-40 and 5W-40 viscosity or thickness in operating or hot temperatures. At an operating temperature, it is important that oil is in a balance between thin and thick. The number is the same across the two engine oils, meaning both engine oils thicken at the same amount during hot temperatures to protect engine components and improve efficiency.

0W-40 vs. 5W-40 Grade

The Society of Automotive Engineers (SAE) designed a grading system for oil based on two extreme weather conditions: cold and hot. According to the grading system by SAE, there are eleven grades for engine oil. The grades are represented by the numerical codes before and after “W” in the product name, with the first number representing the cold temperature, and the last, the hot temperature.

For cold environments, the grade starts from 0W to 25W, while for hot environments, 20 to 60. The engine oil grade gives an idea of how the lubricants will work under differing weather conditions.

Pouring motor oil in car engine.

0W-40 will work better in a cold environment because it has 0 viscosity in cold temperatures and thins better than 5W-40 in such temperatures, making it flow easily. While during hot temperatures, the lubricants have the same grade, 40, which thickens the lubricant enough to provide protection and engine efficiency.

Irrespective of 0W-40 and 5W-40 being different grades, which is evident in cold temperature viscosity, they are nonetheless multi-purpose lubricants capable of working efficiently in both cold and hot environments. 0W-40 and 5W-40 will both perform efficiently in hot temperatures as they have the same grade.

The only difference is in cold environments, with 0W-40 edging 5W-40 because of its lower viscosity. The 0 grade of 0W-40 is better than 5W-40’s 5, making the former thin and flowing faster in cold temperatures. This makes 0W-40 the better option, especially if you live in a cold region.

0W-40 vs. 5W-40 Performance

The performance of both lubricants is another metric to consider when deciding on which lubricant choice to make. The weather, or the surrounding environment, is an important factor used to measure performance. In terms of performance, 0W-40 edges 5W-40 because of how well it fairs in a cold environment.

During winter or in any cold situation, the better performance of 0W-40 is visible, 0W-40 lubricant can pump the engine to a temperature as low as -40 C. On the other hand, 5W-40 can pump the engine to about -35 C, which isn’t as low as the former. The engine will have to pump harder with 5W-40’s high viscosity compared to 0W-40’s low viscosity.

This makes 0W-40 perform better in cold seasons like winter when compared to 5W-40. Nonetheless, this doesn’t mean 5W-40 won’t be efficient in the cold season, not just as much as 0W-40, especially when the stakes are high and the weather is harsh.

The performance of the two lubricants in a hot environment is consistent. The lubricant grade will reach a value of 40 when hot, making the viscosity equal. As a result, 0W-40 and 5W-40 both have similar performance in a hot environment The lubricants will also have high performance for diesel engines, which get very hot when running.

If performance is the only yardstick to be used to judge the best engine oil between 0W-40 and 5W-40, the former comes out as the best once more. It has better performance in cold temperatures than 5W-40 while maintaining similar performance in hot environments. So, if you want an engine oil that will work efficiently in both the harsh winter and summer seasons, then 0W-40 is the better option out of the two.

0W-40 vs. 5W-40 Price

The price is another important metric I will use in comparing 0W-40 and 5W-40 lubricants. However, this criterion won’t be a great determining factor as the differences in price aren’t significant.

In addition, the price of the lubricant also varies depending on the brand. Because there are many brands producing 0W-40 and 5W-40, I won’t be highlighting all the various brands’ prices but giving a general idea of which lubricant is more expensive and the reason why it is.

There are different brands producing 0W-40 and 5W-40 lubricants on the market today. There are some brands with a slight difference in price between 0W-40 and 5W-40, like the Pennzoil Ultra Variation, Castrol, on the other hand, has a higher price difference. Nevertheless, any disparity in price, either within a brand or across different brands, tends to tilt towards 0W-40 lubricants, making them more expensive.

Car driving on a snowy road.

The viscosity of engine oil also plays an important role in its price. The broader range of viscosity in 0W-40 means that it is often more expensive than 5W-40, even when prices are determined by other factors such as brands and types. The slightly higher price of 0W-40 hasn’t stopped it from being popular among car owners as a result of its high performance in extreme weather conditions.

0W-40 vs. 5W-40 Fuel Economy

The fuel economy of 0W-40 and 5W-40 lubricants will be the next basis I will be used to compare the two engine oils. The viscosity of 0W-40 during cold conditions means that the engine strains less to move because the oil is thin and doesn’t need to pump harder.

Sadly, 5W-40’s high viscosity in a cold environment means there is strain and difficulty in pumping, especially when compared to 0W-40. As a result, the ease of movement while using 0W-40 means the engine doesn’t exert much force and consumes little fuel in return. This makes 0W-40 more fuel-efficient and 5W-40 less fuel-efficient when compared with one another.

Engine oil with a lower viscosity grade, such as 0W-40, is slightly better in regards to fuel economy than 5W-40. With the global supply of fuel reducing every year and prices soaring, it is imperative to have engine oil that won’t use as much fuel.

So, to safeguard fuel economy and spend less on fuel, engine oil that won’t use as much fuel is the best option. If every car or automobile owner makes a conscious effort to only select low viscosity engine oil, it will go a long way in saving fuel economy.

However, 0W-40 and 5W-40 won’t make a noticeable difference in the fuel economy because the only difference in their viscosity is during cold conditions. Lower viscosity might translate to some fuel savings, but when comparing 0W-40 and 5W-40 in terms of saved fuel, the difference is marginal.

Can I Use 5W-40 Instead Of 0W-40?

There are some factors to be considered when choosing engine oil for your car. One is the manufacturer’s recommendation. 0W-40 viscosity oils are often recommended by European and American car manufacturers because they provide faster flow in the engine and are also suitable for the weather.

Nevertheless, there are some manufacturers in some regions or countries who will recommend 5W-40. If the manufacturer recommends 5W-40 for your automobile, then you should go ahead and use it. Conversely, if the manufacturer in the owner’s manual specifically mentions not to use 5W-40, then you shouldn’t. Consulting the owner’s manual might be a great place to find out if you can use 5W-40 instead of 0W-40 or not.

However, if you have been using 0W-40 and want to substitute it with 5W-40, you can also go ahead, as the lubricants share almost the same characteristics and can be used interchangeably.

Substituting between the two lubricants might be due to a number of factors, which include availability and cost. Irrespective of your reason, you can use 5W-40 during hot temperatures and switch to 0W-40 during freezing situations.

In addition, if you live in a country or region that doesn’t experience harsh winters, you can also use 5W-40 instead of 0W-40.


There is no wrong answer when it comes to the choice of engine oil between 0W-40 and 5W-40. The factors to be considered depend on temperature performance, price, viscosity, and fuel economy, although the differences based on these highlighted criteria are not overly significant.

This shows the high similarity between 0W-40 and 5W-40 and how they can be used in different weather conditions and interchangeably, even though the former might have an edge based on its lower viscosity and higher performance.

The intent behind this blog article is to answer most of your queries regarding 0W-40 and 5W-40. If you have come this far, thank you, and I hope a clear picture is presented and your questions are answered.

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About Matthew Webb

Hi, I am Matthew! I am a dedicated car nerd! During the day, I am a journalist, at night I enjoy working on my 2 project cars. I have been a car nerd all my life, and am excited to share my knowledge with you!

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