Best 5W40 Oils Review 2021

W40 Oil – Buying Guide, Opinions and Analysis


Car oils protect and maintain the properties of your engine for longer, so it is very important to pay attention to the type and characteristics of the product before making the purchase. Among the most popular 5W40 oils of the moment are Repsol RP135X55 Elite , which is specially developed to achieve better stability in terms of viscosity, as well as optimal fluidity at low temperatures. Another product of interest to many netizens is the Castrol 15C9CA Magnatec , a high-quality product that forms a highly durable protective layer from the moment of startup.


Shopping guide


After the passage of kilometers and time, the oil in cars deteriorates, losing its viscosity properties, which reduces the protection of the engine. That is why every certain mileage the appropriate lubricant must be changed to guarantee the correct operation of your vehicle’s engine.

If you do not know many lubricants and do not know where to start to choose the appropriate one for your car, we have prepared for you the following guide to buy the best 5W40 oil, where we mention the most important aspects that you should look at before making your choice. .



If when choosing the next oil for your vehicle, the first question you ask yourself is: how much does it cost? It is because you will surely be interested in buying the cheapest oil, either because you have a reduced budget, or because you do not want to invest too much in the lubricant.

However, it is important that you consider the importance of using a good oil with your engine, since it is in charge of adequately protecting the metal surfaces, avoiding premature wear of the parts. In addition, because oils lose their properties over time, it is necessary to consider purchasing a product that guarantees good protection for a longer time, distancing the need for each maintenance and reducing the long-term investment.

Therefore, before you want to save a little money and buy the cheapest lubricant, it is advisable to spend a little more and buy an oil that adequately protects your vehicle’s engine.


SAE grade

To measure the viscosity level of a car oil, there is a scale known as SAE grade, which determines the viscosity based on engine temperature. In theory, the higher the number, the better the viscosity will hold at very high temperatures.

However, it is important that the lubricant is fluid when the engine is cold, to ensure that it is distributed correctly throughout the engine and, in this way, can adequately protect the internal parts that are in constant motion, which favors the start. This means that the oils change their level of viscosity according to the temperature at which the engine is working.

In this sense, the SAE regulation establishes two levels of viscosity, the first number that is accompanied by a W (Winter) indicates the behavior at low temperature, while the second number refers to its reaction to high temperatures. Also, while a low number indicates that the lubricant is more fluid, a high number will be more viscous.


ACEA regulation

Another of the most important factors that you should consider when choosing a new lubricant is its ACEA standard, which refers to a series of minimum criteria on the behavior of a motor oil according to the Association of European Automobile Manufacturers, for vehicle models. gasoline, diesel and equipped with particle filters.

For gasoline or diesel cars, ACEA levels can be A1 / B1, being of standard quality and adequate to save fuel. A3 / B3, which does not have the fuel economy requirement. A3 / B4, a level that indicates a high level of quality for synthetic and semi-synthetic oils. And finally, A5 / B5 refers to the highest level of quality, as well as being fuel-saving oils.

On the other hand, for cars with particle filters, the ACEA level is shown next to the letter C. Therefore, if it is C1, it is an oil with a very low ash content and economizing characteristics. made out of fuel. C2 refers to a high-quality, low-ash oil, as well as fuel-saving properties. C3 and C4, for oils with low or very low ash content, respectively.


API classification

On the other hand, there is a classification that determines the quality level of the lubricant, so it is another of the factors that we recommend you review before making the purchase of your next car oil.

Its levels are: SH, SJ, SL, SM and SN.

SH : Indicates better protection against oil oxidation, wear and corrosion.

SJ : Maintains greater fluidity at low temperatures, protecting the engine from high engine speeds.

SL : Refers to better resistance to high temperatures and wear.

SM : It is specially developed for gasoline engines, improving fuel consumption.

SN : Generates greater protection against emission control systems.




Frequently asked questions


Q1: How to change the 5w40 oil?

To change the engine oil in your vehicle, you have two general methods available: through the crankcase or by aspiration.

In the first, it is the traditional way of changing the oil in a vehicle, since it is done by removing the corresponding lower plug to drain the entire tank. The first thing you should do is start the engine for a few minutes, since the change must be done with the oil at a high temperature.

Using the appropriate wrench, continue removing the drain plug commonly found under the engine. In case your vehicle is Smart, you will know that its engine does not have a cap, so the procedure is carried out by aspiration.

In the first case of vehicles, remember to place a container just under the cap. Also, to protect the floor, you can put some newspaper around the container.

When removing the plug, you will need to be careful, as the oil can be a bit hot. Proceed to remove the filter and wait the necessary time for all the oil to come out. Grease the rubber of the new filter and insert it in the place where the old one was, remembering to replace the drain plug.

Finally, remove the oil filler cap and apply the necessary amount of clean oil.


Q2: Every how many km is the 5w40 oil changed?

According to all the specialists, there is no fixed number of kilometers with which you can guide yourself to know the perfect time to change the oil in a car. To know the right time to change the oil, a series of important factors come into play, such as the brand, type, year of manufacture and even your driving style.

Many manufacturers indicate a clear series of recommendations, so you have to look at the technical specifications of each vehicle model carefully. For example, if you own a Ford vehicle, you should consider that there are models that should have the oil changed every 10,000 kilometers approximately. Whereas if you have an Audi, you will know that the oil is changed every 50,000 kilometers approximately.

However, as a general rule, it is recommended to change the oil from 15 to 20 thousand kilometers, if your vehicle was manufactured after the year 2000, and from 7 to 10 thousand kilometers, if it is before that date.


Q3: Which oil is denser: 5w40 or 10w40?

Taking into account the SAE regulations, we know that the numbers next to the W refer to the limit action temperatures under which lubricants work properly, indicating their state of viscosity or fluidity.

In this sense, 5W40 oil is a lubricant twice as fluid as 10W40, allowing easy access to the moving parts of the engine. However, both are just as dense when running on a hot engine.


Q4: What temperatures does 5w40 oil withstand?

Considering that the first number indicates the cold temperature and the second the hot temperature, 5W40 oils withstand a temperature of 5 degrees Celsius in cold or “winter” and 40 degrees Celsius when hot or with the engine running. 


Q5: Which oil is better 5w30 or 5w40?

It is not about which is the best, but which is more or less dense than the other. We already know that the second value indicates the label on the SAE regulations of a particular oil, it refers to its viscosity. Therefore, a 5w30 oil will be much less dense than a 5w40 oil, which means that it is less viscous. However, it also refers to the maximum temperature in Celsius at which the lubricant works optimally.


Q6: What happens if I mix a 5w40 oil with a 10w40 oil?

While some users warn that it is not good to mix types of oil and, in case you are going to apply a different one, you must first remove all the previous one, the truth is that, if there is not much difference between the viscosities, it should not cause damage to the engine.

However, it will always be more reliable to apply the same type of oil on one already inside, in addition to that if you have the possibility to completely remove the previous one, it will guarantee that there are no residues or ash remains.


Q7: Where to dispose of used 5w40 oil?

Car oil is recyclable, so there are suitable places to deposit used car oil, for which you will have to store it in a safe, clean container that closes well to avoid leaks. In many localities, a series of containers have been installed where you can deposit it.




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