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Can You Add Oil To a Hot Engine?

Can You Add Oil To a Hot Engine?

You might have heard that it is dangerous to put oil into an engine while it is still hot. So, can you add oil to a hot engine? 

You can add oil to a hot engine as long as you do so safely. Since your engine is durable, rapidly cooling the engine with oil is harmless. 

As long as you take care – and generally only are topping your oil off – it should be safe to add oil to a hot engine.

Why Is It Supposedly Dangerous to Add Hot Oil to an Engine?

Some people have heard that you can deform or crack your engine if you add oil to it before letting it cool off. This is because when an object heats or cools rapidly, it might change shape a little or crack.

Mixing hot and cold temperatures can certainly damage an object. For example, you might break a glass if you pour boiling water into it. Will cracks form in your engine?

Your Engine is Not Delicate

Unlike a glass, a car engine can handle extremes of temperature. Lowering the temperature a very little bit by pouring oil into it won’t crack or deform the engine. The temperature difference won’t do any damage. 

Things expand when they get hotter and shrink when they get cooler, including engines. However, engine oil isn’t enough to cause rapid cooling that will damage the engine. 

Engine oil cools the engine slowly. Your engine’s parts are durable and flexible. Even if you add oil to a hot engine many times, it won’t hurt your car. 

What Is a Car Engine Made of?

What is a Car Engine Made Of

Different parts of your engine are made from different materials. Car engines are made of cast iron alloys and aluminum alloys. Spheroid graphite and titanium are also used to build car engines. 

Don’t Overfill Your Engine

Pay attention to the min/max markings to avoid overfilling your engine. Your engine can hold about a quart of oil. Add about 1/8th of a quart (118ml) each time and you can fill it up without spilling oil. 

What Does Oil Do for Your Engine?

Mostly, oil keeps your engine lubricated so it can move without seizing up. Moving mechanical parts may not work and will break without oil.

Cleaning Your Engine

Oil also keeps your engine clean. Your engine produces small amounts of soot and dirt which would eventually clog pathways. 

Engine oil contains ingredients that prevent clogs. Engine oil will slowly turn black if you use it for a long time. 


Overheating can permanently damage an engine. Many parts of an engine are designed to be able to cope with extreme temperatures. 

However, an engine can still overheat and this can leave it too damaged to repair. If an engine severely overheats for a minute, less than a minute, or sometimes even a few seconds, that can wreck it. Always pull over right away if the engine temperature is too high. 

Engines have oil pumps that make sure oil gets to every part of the engine that needs it. The oil helps keep the engine cool when it has been running for a long time. 

What Happens When Your Engine Runs Out of Oil?

Very low oil can also wreck your engine. In less serious cases, insufficient oil might increase wear and tear on the engine or do damage that can be repaired. Low oil leads to low oil pressure and high temperatures. 

When oil is too low in an engine, the oil’s molecular structure will change. This will make it stop working as lubrication. 

How Often Should You Add New Oil?

Some cars need new oil about once every 1000 miles. However, it can be more or much less often than that depending on how much oil your car burns. 

Some cars and trucks need a quart every week, others half a quart each month. There is no good average figure to use. 

Give your vehicle oil if it needs it. Check your oil regularly and add more oil when needed. Keep the oil between the two marks on the stick and don’t let it go below or overfill it above the lines. 

Older Engines Need More Oil

When an engine is new, it hardly uses up any oil. A small amount of oil is burned up during combustion, but not much. As the engine ages, the loss of oil increases. 

How Often Do You Change the Oil

Key Takeaways to Adding Oil to a Hot Engine

It is safe to add oil to a hot engine. You don’t have to let your engine cool off first. 

Some people think that cooling the engine rapidly by adding oil when it’s hot could crack the engine. However, this won’t happen because the engine is durable/flexible and can handle swings in temperature. 

You need to add new oil to your engine somewhat often. You can permanently wreck your engine if you let the oil get too low. 

Zach Reed

Hi, I'm the founder of! Having owned a wide variety of vehicles in my life, I was astounded at how hard it can be to find answers to common automotive questions. Rather than sit idly, I decided to create this website to help others!