5w40 vs 15w40

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A vehicle is comprised of many internal engine parts that are interconnected with gears and gliding mechanisms. Therefore, they need frequent lubrication while they run on roads to ensure less friction between them.

And here comes the necessity of motor oils to serve the purpose. 5w40 and 15w40 are two popular types of motor oils that are used for maintaining automobile parts.

First, however, you need to know the differences and specifications of both these oils to choose one for your vehicle.

5w40 vs 15w40

Getting the right motor oil is quite a complicated job when you don’t know the specifications you need to consider. If your vehicle manufacturer has given you two options, 5w40 and 15w40, to choose from, and you are in confusion about choosing one among them, then this 5w40 vs 15w40 article is there to help you out. 

5w40 Specifications

5w40 motor oil has got its name from the oiling process that is carried out with its utilization. The numbers within the title of this oil signify the weight, thickness, and viscosity. The number ‘5’ indicates the overall viscosity rating for the oil at low temperatures, and the number ’40’ indicates the overall viscosity rating of the oil at high or operating temperatures.

The viscosity rating of 40 indicates that this motor oil is efficient to pump the engine even at a high operating temperature of up to 100 degrees Celsius. Also, this oil is highly viscous to ensure that the flow is ideal for reaching out to all the engine parts quickly after the initial start-up.

Pouring oil to the engine with a black funnel

And, the low-temperature viscosity of ‘5’ indicates that the oil is ideal for vehicles to start up even at -30 degrees Celsius. Hence, this is what makes this oil a popular choice on the list. 

It comprises active detergent and has high oxidation & thermal stability. In addition, it supports low fuel consumption and suppresses the sludge build-up. It also resists oil aging and offers long-term protection.

This oil also has high viscosity index that indicates its efficacy. Furthermore, the service life of the engine will improve with the use of this oil. It is suitable for vehicles with all riding styles.

Irrespective of riding your vehicle in a cold or hot climate, this motor oil has properties to help keep the engine running seamlessly. Even though 5w40 is a thick oil, there is no obstruction in its flow over the engine parts.

15w40 Specifications

15w40 engine oil is yet another one in the competition that makes the motor system function efficiently. It is multi-grade oil that has a base of mineral oil. Moreover, the numbers 15 and 40 denote the oil’s weight, thickness, and viscosity at low and operating temperatures.

For example, the number 15 indicates the rating of viscosity of the oil at low temperatures. And, the number 40 indicates the viscosity rating of the oil at high or operating temperatures. 

It means that this oil is also stable to use in vehicles that operate in both summer and winter climates. Therefore, this oil can be used ideally for vehicles throughout the year. Furthermore, this motor oil is ideally preferable for all gasoline and diesel engines, on priority. 

Cans of engine oils stacked

In addition, this motor oil also has high oxidation and thermal stability. Apart from that, it promotes advanced dispersancy and prevents sludge formation. Furthermore, it neutralizes the acid and controls the deposits to protect engine parts from wear and tear.

By using this, you can expect to have a better oil pump and clean engines. In addition, it will increase the life of all of the engine components, thereby ensuring that your vehicle showcases optimal performance.

Similarities of 5w40 and 15w40

  • Both of these oils have high thermal & oxidation stability.
  • These oils have the potential to avoid the build-up of sludge within engine components. 
  • The operating temperature viscosity is the same, with a rating of ‘40’ for both these oils. 
  • Both these oils extend the service life of the engine.

Differences of 5w40 and 15w40

  • 5w40 is full synthetic engine oil, whereas 15w40 is synthetic blend engine oil. 
  • 5w40 provides extra wear protection, whereas 15w40 provides triple protection. 
  • Also, 5w40 oil is quite essential for use only in winter climates. However, the 15w40 oil is ideal to be used in winter and the summer climate.
  • 5w40 offers extra detergents to fight deposits and sludge, whereas 15w40 has exceptional deposits for cleanliness and control. 
  • 15w40 offers better shear stability and oil flow at low temperatures. And, 5w40 offers a quick start and quick protection in a cold climate. 

Major Distinguishing Factor

The operating viscosity of these motor oils is the major distinguishing factor. For example, the operating viscosity of 5w40 is 3.8 to 12.5mm2/s, whereas, for 15w40, it is 5.6 to 12.5mm2/s. Hence, it states that 5w40 is a better and expensive oil than 15w40 due to its viscosity level.

An old car engine with wires and an oil depository

When to Use 5w40?

5w40 is quite the best pick for any vehicle, close to 5w20, that operates mostly in winter climates, in contrast to 10w40. It is because the cold start-up of the vehicle is quite proficient with this oil, in comparison to 15w40. Moreover, 5w40 is also ideal for helping you improve your fuel efficiency by 1 or 2%. So, consider this aspect for using it as well! 

When to Use 15w40?

15w40 oil is more apt for high-temperature regions. Therefore, you need to keep in mind that if your vehicle goes through frequent commutes over a long distance and the engine heats up very often, this is the perfect oil for lubrication.

Even though the viscosity index is high for low temperatures, it still performs well for cold regions. However, it is not as reliable as 5w40.

Final Verdict

If you intend to choose the best oil for your vehicle, considering some key specifications is essential. Firstly, check the manufacturers’ manual to know the suitable oil for your vehicle. For example, if 5w40 and 15w40 are ideal for your vehicle, consider the specifications, and decide the best one for the engine since this is a garage and car essential.