Mixing Hot And Cold Cooking Oil: Is It Safe?

Mix cold and hot cooking oil

Whether you are pan-frying, deep-frying, stir-frying or sautéing, it sometimes happen that you need to top up your cooking oil.

We all know that adding any liquids, especially cold ones, to hot cooking oil, can cause some serious reactions.

This is especially true in the case of water added to hot cooking oil.

So is that also the case for cold cooking oil? Can you add cold cooking oil to hot cooking oil?

The answer is a definite “Yes”. You can add cold cooking oil to hot cooking oil. However, there are exceptions, and I will cover these below.

In this article I will discuss:

Can you add cold cooking oil to hot cooking oil?

Yes, with a few exceptions, you can safely add cold cooking oil to hot cooking oil.  
It’s normal for your oil level to drop while cooking because foods absorb oil.
This rate of oil absorption differs between foods and also depends on the temperature of the oil.

The hotter your oil, for example, the more oil is absorbed.

These oils are needed for effective heat transfer.

So as the oil in your pot or pan decreases, the less heat transfer material is available.

This is when the risk of burning your food increases.

The easiest and most straightforward way around this is to top up your oil.

Just add the necessary amount of oil to get to the desired level and voila.

There are, however, certain precautions to take and things to bear in mind.

Do not top-up hot cooking oil with oil that contains water

Water and hot oil DO NOT GO TOGETHER.

This is a very important thing to remember.

When you add water to hot oil, a violent reaction occurs.

I will cover this in detail in another article.

But in short, when you add water to hot oil, the water will sink.

Water and oil don’t mix due to their chemical properties.

When the water sinks, it starts to heat up rapidly and expand rapidly.

This in turn causes it to erupt and spray hot oil everywhere.

So when you want to top up your hot oil with cold oil, make sure the cold oil does not contain any water at all.

If it does, the same reaction described above will happen and could have some serious consequences.

Do not top up hot oil with older oil

As we all know, oil can be used several times over.

There are no serious issues when you use the same oil a handful of times, other than the change in the taste of the oil, and thus also the taste of your food.

When you use the same oil several times, it eventually starts to change colour.

That is due to food particles tainting the oil.

This goes hand in hand with the taste of the oil being impacted.

And eventually after several uses, the oil will go rancid.

So if you are cooking up a storm, you don’t want to ruin your dish by adding older oil, unless it is from the same oil you started off with.

There are no serious health issues with this, it will just negatively impact the flavor of your food.

When you top up hot oil, do it slowly and evenly

Don’t just dump the oil you need smack in the middle of the pot or pan all at once.

Do so slowly and evenly all over the cooking surface.

And also do not add it straight on top of the food you are frying.

Remember, oil is the medium for heat transfer.

If you add it too quickly and in one spot, it will cool down that spot while other parts of the pot or pan are still hot and doing its job.

This causes heat imbalances in your dish and could cause uneven cooking.

So add the oil slowly while at the same time spreading it out.

The temperatures in the oil will even itself out quicker this way and you’ll have even heat distribution and thus an evenly cooked dish.

Another reason to add the cold oil slowly and evenly, is to prevent any oil spilling and splattering out of the pot or pan, especially when it is hot and can burn you.