You might have difficulty checking the engine oil level if you own a car. Some say you should check it when the engine is hot, while others should check it once cold. There might be a possibility that you have heard people saying engine oil expands or contracts when hot or cold, and this would have landed you in a lot of confusion.

We will try to clear up your confusion in this article today. Let us see: does engine oil expand when hot or not?

Does Engine Oil Expand When Hot?

Almost everyone has read this scientific concept of the expansion of liquids at high temperatures, which also applies to engine oil. Like other liquids or fluids, engine oil does expand when hot. Something to note here is that it can break down if it gets too hot, which means instead of getting expanded, it can practically contract after a particular temperature instead of getting expanded. 

Your engine oil also evaporates when it breaks down, so that will be a noticeable change if you miss it.

Let’s understand the concept behind engine oil expanding when hot.

Why Is It Said That Engine Oil Expands When Hot?

If you have heard someone saying engine oil expands when hot, yes, you have heard that right. Engine oil does expand a bit when hot, and it is said so because liquids practically acquire space between the molecules when heated. The concept behind this is the thermal expansion due to kinetic energy.

What Causes Engine Oil To Expand When It Is Heated?

When we drive the car, the engine gets heated, and the engine oil present in the pan starts flowing through the filter to the parts that need them the most at that moment to run smoothly. While those parts are continuously in motion, they get heated and heat the oil. 

The energy created by the motion of those parts gets converted into heat energy and increases the temperature of engine oil. This continuous process keeps the oil inflow, and as a result, kinetic energy space is created between the molecules of engine oil, which causes it to expand. 

Engine oil expands because its molecular bonds are often weaker than solids. When molecules are heated, they travel quicker and flow to different parts. Now you might be wondering whether there will be a visible change in engine oil level.

Let’s have a look!

Is There A Visible Change In Level Of Engine Oil When It Is Hot?

You can see a bit of change in the oil level when hot. Still, it is always advised not to check the engine oil level right after you have stopped your car. If you are curious to know whether there is a change in the engine oil level due to expansion, you can do that by taking the help of a dipstick but at your own risk.

It is always advised to wait for at least 5-10 minutes before checking the engine oil after you stop the car because the expansion is temporary, so once the oil starts getting to normal temperature, that will give you the exact idea about the level of the engine oil in your car.


When we drive, the car engine gets heated, and the engine oil present in the pan starts flowing to the parts, which makes it heated as a result and as mentioned above, engine oil expands when hot. 

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