15W-40 Engine oil: Everything You need to Know

The purpose of engine oil is to keep the engine running well. It keeps the moving parts from getting worn down by friction. It also prevents rust, corrosion, and other dirt from getting into the engine.


It also prevents rust, corrosion, and other dirt from getting into the engine. Since different engines have different requirements, engine oils come in various grades. Based on how thick the oil is, these grades are made. Each car has a recommended grade of engine oil that should be used to get the most out of it. 


15W-40 is a common grade of engine oil that is often suggested for diesel engines. The thickness of oil changes based on how hot or cold it is. Oil tends to get thicker when it’s cold, and when it’s hot, it thins out. This is why there are two numbers on engine oil grades.


This is why there are two numbers on engine oil grades. In 15W-40, the first number, 15, shows how thick the oil is when it is cold. So, it is followed by the letter “W,” which stands for “winter.” The second number, 40, shows how thick the oil is when the temperature is high.

How is 5W-40 oil different from 15W-40 oil?

As was already stated, engine oils come in different grades based on their thickness. Each grade of oil has two numbers showing how thick it is when it is cold and hot. In general, the oil is thinner when the first number, which comes before the W and shows how thick it is when cold, is lower. 

Also Read:  What is the Role of Engine Oil?

Since 5 is less than 15, which means thin, 5W-40 grade oil is thinner than 15W-40 grade oil. Viscosity is the biggest difference, but there are some others as well. For example, 5W-40 is a grade that is only found in fully synthetic oil, b
For example, 5W-40 is a grade that is only found in fully synthetic oil, b 

Also, most diesel engines use 15W-40, while most gasoline engines use 5W-40. This also means that, depending on the type of fuel it is meant for, the additives have different profiles.

Can I replace 5W-30 with 15W-40?

Every engine has its own needs when it comes to engine oil. These things depend not only on how the engine is made, but also on the model of the car, the fuel used, how it is used, how big the vehicle is, and so on. 

This is why there are different grades of engine oil based on how thick they are. Every car and bike comes with an owner’s manual that tells you what grade of engine oil works best for that model.

Car owners should use the recommended grade of engine oil to get the most out of their engine and avoid problems. Since 5W-30 and 15W-40 are different grades with different thicknesses, they can’t be used interchangeably. 


Most of the time, 15W-40 is good for diesel engines because it has a lot of additives that protect against wear. On the other hand, 5W-30 is often suggested for gasoline engines, and its additive profile is different.

Also, they are very different in how thick they are. For example, 15W-40 is a lot thicker than 5W-30. Because of this, you shouldn’t use one instead of the other, and you should always use the grade of engine oil that the manufacturer recommends in the owner’s manual.

Also Read:  How Long to Let the Engine Cool Before Changing the Oil?

Is it better to use 15W-40 than 10W-30?

The grades of engine oil are 15W-40 and 10W-30. The viscosity of 15W-40 is higher than that of 10W-30. Both thick and thin oils have their pros and cons.

Thicker oils offer more protection because they create a thicker layer between the moving parts inside. Because of this, there is much less friction, and the parts don’t wear out as quickly. On the other hand, it takes more energy for the engine to pump thick oils because they are harder to move.

This changes how well the car uses gas. Thin oils have less resistance and are easier to move around, saving more fuel and getting better gas mileage.

Thin oils have less resistance and are easier to move around, saving more fuel and getting better gas mileage. Thin oils, on the other hand, might not last as long or protect as well as thick ones. 

What kind of oil to use depends on what the driver wants. For example, someone who drives an old car might want more protection and choose a thicker oil. In the same way, someone who wants more miles per gallon would choose thinner oils. 

Also, the oil you choose depends on how hot or cold it is when you drive. Since 10W-30 is quite thin, it might be better in colder weather, while 15W-40 would be better in hot weather.

There is no one answer to the question of which of these two oils is better. It depends on the situation. So, it’s best to read the owner’s manual and use the engine oil grade that the manufacturer suggests.

Leave a Comment