How Long To Let An Engine Cool Before Adding Oil

ByKern Campbell

Are you interested in how to safely keep up with your vehicle’s maintenance? Adding oil and changing the oil at regular intervals is just one way to keep your vehicle running smoothly and at an optimal level. This way, you can extend the life of your automobile by handling this task yourself at a lower cost. 

How Long To Let An Engine Cool Before Adding Oil 1 1 How Long To Let An Engine Cool Before Adding Oil

Table of Contents

How long should you let an engine cool before adding oil?

Generally, letting your car’s engine sit and cool for 20 to 30 minutes before adding oil is adequate. This interval provides enough time for the oil cap on the reservoir to cool and the existing oil to drain through the lines for an accurate reading. 

To ensure you avoid burning yourself on the oil cap or hot engine parts, let the vehicle cool down before attempting to add oil. Of course, there are other considerations before tackling this job, but having a cooler engine is one significant element. 

Of course, the local climate and how long your vehicle has been running will impact how long it will take to cool down. 

For example, starting your automobile and moving it to a better spot to add oil will not require much cool-down time. However, this is often not the case, so this guide ensures you can complete this task safely. 

Do Not Add Oil When a Vehicle Is Running

Although the motor oil should be slightly warm to avoid overfilling the reservoir, it should not be extremely hot or running during this task. If you try to add oil to the engine while it is running, you are putting yourself and the engine at risk.

Some adverse situations that can occur when trying to add oil to a running engine are: 

  • The engine components will be too hot to touch
  • The oil will be hot and can cause burns
  • The oil can splash out of the reservoir onto the engine, causing it to smoke or even a fire
  • There are moving components in the engine that can come into contact with a funnel or oil container, causing damage
  • Other moving engine parts, such as the cooling fan, can catch on clothing or your hands, causing harm

Why the Engine Should Be Cool

There are several reasons why it is recommended that you should allow the engine to cool down before adding oil. 

Although some believe that adding oil to a hot engine may cause damage, it is safe to do. However, it can cause symptoms like smoking or a burning smell as it goes into a hot engine. Thankfully, this minor side effect will disperse quickly, and the vehicle will resume effective operation.

Some vital motives for this step include the following: 

  • Engine components are hot to touch 
  • Dipstick oil reading may not be accurate 
  • Ensures you won’t overfill the reservoir 
How Long To Let An Engine Cool Before Adding Oil 1 How Long To Let An Engine Cool Before Adding Oil

Engine Components Are Hot To Touch

Burns are a common concern for many individuals working on vehicle engines. Some components under the hood do not have protective covers and will retain heat from the engine as it runs. 

Pieces like the oil cap can contain aluminum and heat-resistant plastics. Although these parts will not melt or become damaged from consistent heat, they will hold heat for a few minutes after a vehicle shuts off. 

Letting the engine cool slightly will ensure you do not burn your hands or arms when working under the hood when adding new oil to your vehicle. 

Dipstick Oil Reading May Not Be Accurate

When oil is extremely hot, it becomes thinner and less obvious to see on a dipstick. Checking the oil right after you turn off a vehicle will result in some oil remaining in the lines and require time to drain into the oil pan. 

Allowing 20 to 30 minutes to pass after operating a vehicle allows the oil to cool down so you can see it on the dipstick easier and don’t burn yourself checking the levels.

Ensures You Won’t Overfill the Reservoir

Because oil expands with heat and becomes thinner, it can be challenging to read a dipstick if the engine is too hot. In contrast, if the engine is too cold, the oil may be in a condensed state and provide a lower-level reading that isn’t accurate. 

When the engine is cooler but not cold, the oil will settle into the reservoir adequately and remain in a state that is easy to read and precise. Having a clear reading on a dipstick can help you guarantee you will not overfill the reservoir when adding oil. 

Overfilling your engine oil can create pressure on the crankshaft, resulting in air bubbles and foam entering the system. The resulting effects can allow extra oil to enter these areas where it shouldn’t, causing overheating and engine damage. 

Should the Engine Be Cold Before Adding Oil?

The type of oil your vehicle uses will impact how it flows through the engine. Some synthetic brands will compress in cold circumstances and expand in warmer temperatures. Therefore, if your climate is extremely cold, adding oil to a cold engine can pose a risk of overfilling the reservoir. 

If your vehicle is completely cold, it is best to start it for a few minutes to warm it slightly before turning it off again. You don’t want to run it too long where the oil cap retains heat that you cannot touch it. A warmer engine allows the oil to flow through smoothly and will provide a more accurate dipstick reading. 

The Takeaway

If you are interested in performing helpful automobile maintenance tasks, like adding oil, knowing the proper method will ensure you remain safe and complete it effectively. Although you can add oil to your vehicle when the engine is hot, it is not recommended because of extreme temperatures. 

It is best to add oil to your engine after letting the engine cool down for between 20 to 30 minutes. This timeframe helps provide an accurate dipstick reading while allowing the oil cap and other engine parts to cool so you can touch them without injury.