Should Car Be Running When Adding Oil? (Important Facts)

As a driver, you may start wondering about the things related to your car’s maintenance from time to time. One of these questions concerns oil, about whether you should add oil when the car is running or not. So, you may ask:

Should a car be running when adding oil? The short answer is no. Any car that you’re about to add oil to should have its engine off to cool down. The heat from a running engine is too hot that it can burn your skin if you touch it by accident. Moreover, you’ll need the oil to get cold so you can measure it accurately.

In this article, we’ll cover a list of questions related to this matter. This way, you can understand the difference between the two and the risks of the other. It will also give you an idea of how you can add oil most efficiently.

Without further ado, let’s get into it!

Should Car Be Running When Adding Oil

Do You Add Oil While the Car Is Running?

In general, it’s not ideal for you to add oil while your car is running. The reason is that a running engine would be too hot for you to handle.

For instance, if you’re out for a drive and you’ll need to add oil, you may get burned by touching any engine part by accident, as all of it would likely be piping hot.

Another thing is that the oil in a running engine would be too hot that it will tend to splash on the dipstick. As a result, you won’t get an accurate reading before and after adding oil up.

For these reasons, it’s ideal for you to add oil after letting the engine cool down for about half an hour.

Such a time would also be enough for the engine’s oil to come to a measurable state.

Why Can’t You Add Oil Into a Running Car?

You can’t add oil into a running car because the engine and the remaining oil in it would be piping hot to handle.

Many people think that adding room temperature oil to a hot engine would damage it. However, it’s not entirely true.

Still, it remains the fact that the engine would be hot enough for anyone to handle. For instance, an accidental touch to the engine would result in getting your skin burned.

Moreover, even if you add oil to a running engine, you would need to turn it off and let it cool down to get an accurate reading.

If you don’t do so, the oil in the car will get so hot that it would only splash on the dipstick, giving you an inaccurate reading.

In the end, you need to wait for several minutes before checking the oil level. During that period, the engine would cool down, and it will not be hot when you top it up.

As always, take it as a rule of thumb to get the most accurate reading and refilling. This way, you will avoid overfilling the engine with oil.

Another thing to note is that if you add oil, make sure your car rests on level ground. This way, you’ll also have a better chance to get an accurate reading.

adding oil into running car

What Happens When You Put Oil in a Hot Car?

In general, no harm will happen to your engine even if you put oil in it while it’s hot. However, you may get yourself hurt in the process.

The thing about a hot car is that the engine parts would also be piping hot, and it goes the same with the oil.

If your car came from both a long or a casual spin, the engine and oil would be hot enough for anyone to handle.

Moreover, engine oils in hot temperatures transform into a thin substance. As a result, it becomes flowier, and it tends to splash its way.

For these reasons, you must allow your car to settle down and cool before adding oil.

Now, even if you do add some oil, you’ll still need to wait for it to cool down so you can get a proper reading. Otherwise, you may end up overfilling, which is a bad idea.

Can You Leave the Oil in a Hot Car?

Extreme temperatures can affect the quality of the oil. Thus, it would be ideal for you to protect your car against such.

Both heat and sunlight can change the chemical composition of your engine’s oil. As a result, it may also affect the performance of your engine.

For this reason, it would be best not to park your car in direct sunlight and heat for prolonged periods.

If you can access some shady areas, it will help protect both your oil and engine.

Another thing to note is that too much heat can cause the oil to evaporate quickly. Thus, you should avoid going to such conditions for a long time.


A running car is equivalent to a piping hot engine and oil. Thus, if you plan on topping it up with oil, your best bet would be to allow it to cool down first.

In general, it won’t harm your engine if you add oil to it while it’s running. However, if you do so, you’ll be prone to hurting yourself by the heat and getting inaccurate oil measurements.

For these reasons, always take it as a rule of thumb to let your car rest and cool down before adding oil. This way, you can add oil more efficiently and accurately.



Image credits – Canva

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My name is Hank, and I've been in the automotive industry for 27 years. I've been working in my own auto repair shop for the last 13 years, and now I want to help you here, on my blog. Let me know if you have any questions. Read more