Updated at: 16-07-2022 - By: Lucas

Customers frequently asked me this question when I worked as an automobile engineer in multiple divisions. Adding oil to a hot engine is safe? This article will answer that question.

Even while adding oil to a hot engine isn’t ideal, adding oil to a cold engine is perfectly safe. Even while adding colder oil won’t harm the engine’s metal components, it’s critical that the oil be the same as what’s already in there because mixing different viscosities of oil isn’t usually recommended except under certain circumstances.

When to add oil? In a cold or hot engine?

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Because it’s easier and faster to gauge the proper amount of oil to add when the engine is still cool, this is typically done when the engine is running.

It’s recommended to warm up the engine first in cold weather, especially winter, and then let it to cool down for no more than 15 to 20 minutes if temperatures are below freezing point so that the oil has a chance to settle. The thickened lubricant will restore to its correct fluidity as a result of this preheating.

Afterward, it is possible to correctly assess the oil level. After then, it’s just a matter of combining the new oil with the old to form a uniform mass. Make sure you use the same type of oil when you apply it.

In some cases, such as when the emergency oil pressure light appears on the dashboard while driving, you may need to add oil to a hot engine. As a result, questions like “what will happen if you put cold oil into a hot engine?” are popular.

In the dashboard, or by checking the dipstick, you discovered that the oil level was below the minimum. As soon as it was safe to do so, you retrieved a canister from the trunk and began refilling it.

If you refill the oil while the engine is still hot, you run the danger of adding too much and damaging the engine. Summer is a particularly dangerous time since the engine cools more slowly due to the higher temperatures. However, in the dead of winter, everything changes.

That’s why it’s best to let the engine cool down for at least 15 minutes before adding oil.

When the oil is poured into a warm engine, a temperature difference will be created, but because engine oil absorbs heat at a much slower rate than coolant, it will not cool down as quickly as coolant.

Some claim that cracks may form in the engine’s block, head, or other pieces, as well as other defects in relation to the engine’s various elements. In reality, the only two things to watch out for are overfilling and mixing various viscosities of engine oil.

Adding oil to a car engine. Step-by-step instructions for beginners

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  • So, after making sure of the need for topping up and deciding on the right type of oil you will add to the engine, you will need to put the car on a level surface.
  • Then let the engine cool down, it is advisable to leave the car for some time, and also let the oil drain completely into the crankcase.
  • Now you will oil filler neck or another tool like a funnel to make sure the oil doesn’t reach other parts of the engine. The specified tool is, usually, located under the cover, at the top of the cylinder head. Most often, the lid has a pictogram in the form of an oiler with an icon that resembles a drop of water
  • Next, unscrew the lid, you can also wipe it with a clean cloth and then set it aside.
  • Add the oil filling tool or funnel, or if you don’t have one, cut the upper part of a plastic bottle, this will be enough.

If you have the tool, you may add oil precisely and avoid contaminating the engine’s block and head with oil. High heat, smoke, and foul odors will cause burnout if oil is present on these components.

Engine oil droplets, on the other hand, have a hard time adhering to rubber and other soft components, as well as to all kinds of seals and other engine compartment components. Nevertheless, if oil has been spilled, it is recommended that you completely clean it off as soon as you notice it.

  • Adding oil should be done gradually. This means that 100-200 ml should be poured from the canister at a time. Next, you need to allow it to drain from the cylinder head into the crankcase. This may take about 10-15 minutes. Then the level is checked, after which you can continue to add oil if necessary.
  • When checking the level on the dipstick, you must first remove the dipstick, then wipe it with a clean cloth, then re-insert it all the way into the hole and remove it again. Repeat that procedure 2-3 times to make sure it is the correct level.
  • After the oil level on the dipstick is strictly between the “MIN” and “MAX” marks, it is necessary to firmly insert it into the hole and put back the oil filler cap.
  • The final stage will be starting the engine. Evaluate the operation of the internal combustion engine for extraneous noises, knocks, vibrations. Make sure that the oil pressure light on the dashboard does not light up, or it does not show an insufficient amount of oil.
  • Next, warm up the engine, and make a test drive. After that, it is recommended to let the engine cool down, after which the oil level is checked again. If a decrease in the level is again noticeable, refill it and, as an ultimate solution, check to see if you have leaks.


To avoid engine damage, never drive with low oil levels. If the circumstance warrants it, you can try to fix it yourself until you can get to a repair shop. Using a tow truck is preferable if the oil leaks are particularly severe.

CC BY SA 3.0 (Creative Commons Attribution 3.0 Unported) image by Dvortygirl, via Wikimedia Commons