Updated at: 19-07-2022 - By: Lucas

When it comes to deciding which type of engine oil is best for your vehicle, the debate is long, detailed, and heavily dependent on your vehicle’s engine.

Temperature range and viscosity at 100°C or 212°F are the most significant variations between 10w40 and 15w40 oils. When it comes to engine oils, 10W40 and 15W40 can both be used at temperatures up to 40° C or 104° F, but only 10W40 can be used at temperatures below 20° C.

Engines with a 50,000-kilometer (31,500-mile) or higher mileage tend to utilize both 10w40 and 15w40 oil.

10W40 Vs 15W40 Advantages And Disadvantages

10w40 Vs 15w40.

Inquiries about which sort of engine oil to use are a concern for drivers who have been instructed to do so by a mechanic. This information will not go unnoticed by the driver, as every packing is clearly labeled.

The viscosity of the oil is determined by the marking. Let’s take a closer look at the marks and see which motor oil is recommended.

The viscosity of the motor oil is the most important factor. As the temperature rises or falls, the oil’s viscosity changes, affecting how it spreads throughout the engine.

To be clear, a crude oil’s viscosity class has no bearing on its quality. With regards to viscosity, there are numerous products available from a variety of companies. The quality of each of them varies. It’s impossible to tell how good anything is because there aren’t any related signs. It will be decided in the field.

We have two factors in the 15W40 oil labeling.

15W and 40W. Using the letter W, which stands for Winter, indicates that the oil can be used in the winter as well; it should be used at temperatures no lower than 5° F.

The viscosity, characteristics, and protective features of 15w40 will be retained at these temperatures, allowing the engine to start without issue and guaranteeing good lubrication.

Nevertheless, at a lower temperature, its viscosity will grow, making the oil pump’s function more challenging and even preventing the oil from reaching the friction parts. The engine will wear down quickly as a result of this.

Not at all is it implied that the lowest temperature restriction is set at 15° or five degrees Fahrenheit, as the number 15 is mentioned. Fortunately, this is a one-time occurrence and nothing more. This oil can be used between the temperatures of 4 degrees Fahrenheit to 40 degrees Fahrenheit, or 20 degrees Celsius to 104 degrees Celsius.

There is a lower temperature limit and more fluid oil if you have the first digit lower than the second one in the marking. This value is critical in the winter, but in the summer, a heavier oil, such as 15W40, is preferable.

Because W is present in the oil’s formula, it can be utilized in a wide range of temperatures, from extremely cold to extremely hot. Oils without the W inscription are not to be confused with these, which should not be used below freezing temperatures.

The use of year-round oils has mostly been phased out in favor of universal ones. Since lubrication changes are costly and time-consuming, it makes sense to keep the same lubricant throughout the year.

As shown by the marking’s second number (40), the oil’s highest safe operating temperature is 40 degrees Celsius. In our example, 15W40 oil can work without losing its lubricating properties in a temperature range of 15° to +40°, or 5° F to 104° F.

Which engine oil should you choose?

10w40 Vs 15w40..

The ideal oil for your car’s engine is the one specified in the vehicle’s owner’s handbook. Always follow the manufacturer’s instructions when it comes to adding oil to the engine.

Motor lubricant speed is affected by factors such as the size of oil passageways and other factors. The wrong decision might cause a headache for the motorist and lead to pricey repairs.

The climate where the car is going to be driven also needs to be taken into consideration when selecting the oil. If the weather is chilly, the oil should be more viscous and able to function without issue.

If temperatures fall below 20°C (or 4°F), you should look into oils such as 5w30, 5w40, 0w30, 0w40, and others that can withstand lower temperatures.

It’s also a good idea to check the condition of the engine. As the friction parts deteriorate, the distance between them widens and the addition of a liquid oil will simply flush it away. As a result, older engines benefit from the use of viscous oil.

Older engines, on the other hand, may have carbon deposits and other oil system buildups. Oils containing detergents are recommended for cleaning since they protect the engine and keep dirt and silt from forming.

The driving style should also be taken into account when selecting a lubricant. Oil with a higher viscosity is recommended for aggressive driving, which requires quick acceleration and high speeds. Heavy loads won’t harm the engine because of it.

Despite this, there are many myths about engine oil. Some motorists are of the opinion that 10W40 oil is preferable to 15W40 oil. With that in mind, you can expect a greater or lower cost for the latter.

In reality, the viscosity grade has little to do with the product’s overall quality. The lubricant’s base is not even determined by the viscosity grade. Oils with a viscosity grade of 15W40 can be mineral, semi-synthetic, or synthetic.


10w40 vs 15w40 engine oils have a significant variation in the temperature at which they can be used, however this difference is technically only 5 degrees Celsius or 9 degrees Fahrenheit, but this temperature difference is enough to cause major damage if the wrong oil was used.

If your car has an older engine, these two types of oil are strongly recommended. However, you should also consult your owner’s manual for further information, particularly on ACEA and API requirements.

The complete synthetic, semi-synthetic (sometimes called synthetic blend), and mineral oils available on the market are the best choices, however synthetic blends account for the majority of the 10w40 and 15w40 products on the market.