How Often Should You Change the Oil in a Deep Fryer?

In this brief guide, we will answer the query, “How Often Should You Change the Oil in a Deep Fryer?” and will discuss how many times oil can be reused in the deep fryer?

How Often Should You Change the Oil in a Deep Fryer?

You should change the oil in a deep fryer, after frying non-breaded veggies 6-8 times, and breaded products or fatty meats and fish 2-4 times, replace the deep fryer oil.

According to studies, 25-36% of North American adults consume foods, usually fried, from fast food restaurants every day (1).

How long does deep fryer oil last?

Only use deep fryer oil that has been stored for no more than three months. Allow the unit and oil to cook for two hours once they’ve finished cooking. After that, filter the oil through a cheesecloth or a fine-mesh strainer into a jar. Refrigeration is essential for optimum results, so be sure to cover the container tightly.

It’s important to know how long your cooking oil will last before it has to be replaced.

·         How often do you make use of it?

·         With all that oil, what exactly are you cooking?

·         Do you deep-fry a lot of breaded items?

·         Do you use a certain brand of cooking oil?

You should think about these things before choosing how often to replace the oil in your deep fryer. There is no one-size-fits-all answer to this question.

The high-temperature processing of cooking oils during the production of fried foods leads to the oxidation and production of free radicals, anti-nutritional, and toxic substances in edible oils The formation of phytosterols oxidation products during deep- and pan-frying in vegetable oils for long-duration could have adverse effects on the human health The consumption of repeatedly heated cooking oils causes genotoxicity, carcinogenicity, hypertension, and cardiovascular diseases (2). It could be said that three times of frying could be done with the same oil, but these oils must be filtered after each use and stored in cold conditions, considering the temperature of frying of 180°C and frying time of 3 minutes (3).

What are the most telling indications that it’s time to replace your “old” oil?

The chemical compounds formed during deep-frying changes viscosity, smoke point, and color of the frying oil (2). In practice, physical changes such as dark color, intense smoke, rancid odor, and soapy appearance of frying oil may be the main indicators that it is the appropriate time to discard the frying oil (4).

·         The oil’s surface is covered with foam

·         Fishy smell

·         Compared to previously, there is a significant increase in the amount of smoke produced by the oil

·         A much deeper shade of the original hue.

It’s best to utilize these guidelines as a starting point, but always apply your intuition and good judgment when making decisions.

Is it possible to reuse deep-fryer oil?

Yes, deep fryer oil may be recycled. Filter or cheesecloth the cooled oil into an airtight jar with a cover when it has chilled for approximately 2 hours. For optimum results, place in the refrigerator. Reuse the oil up to 38-10 times before discarding it because the color or fragrance has faded (3).

The Maillard reaction, which occurs in deep fryers, is responsible for the crispy texture of food cooked in them. According to French scientist Louis-Camille Maillard, the reaction is known as the Maillard reaction and refers to a chemical reaction with the oil’s amino acids. This increases the crispiness of the meal while also darkening the color of the oil.

Maillard (non-enzymatic browning) is considered the most important reaction in the browning of food. During frying, this is the main reaction affecting sugars which involves free amino groups of amino acids, peptides, proteins, and carbonyl groups or other aldehydes, and ketones of sugars. Several intermediate products, called Amadori products or pre-melanoidins, are rapidly polymerized at frying temperatures, forming dark-colored molecules (melanoidins). Browning is faster at temperatures above 150 °C. Among all the compounds produced by the Maillard reaction, there is an increasing interest in toxic compounds, like acrylamide. Acrylamide has been known to be a neurotoxic, genotoxic and carcinogenic compound in animals, and is classified as a probable human carcinogen (5).

It’s a shame because the more you do this, the shorter the oil’s shelf life becomes. It was also found that the usability of an oil may decrease depending on the amount of food to be fried, frying temperature, span of frying, and the water present in the environment (3).

When it comes to recycling deep fryer oil, the most effective approach is to clean and store it correctly after each use. When it’s time to clean the oil in your deep fryer (or skillet), follow these steps:

·         Remove any food or dirt using a skimmer.

·         Filter the oil and put it in a clean, dry container.

·         Stop before the oil reaches its lowest point (where there may be more debris)

·         Allow the saucepan to cool fully before covering it.

·         Pour the oil into the original container or an airtight container once again using a funnel.

·         To preserve the freshness of the oil, keep it out of direct sunlight and away from heat sources like a stove.

How frequently should restaurants replace the oil in their deep-frying machines?

Most restaurants with deep fryers will want to replace their oil at least twice a week if they use it often. In certain cases, a single fryer may be devoted to fish or breaded foods, requiring oil to be changed more often.

Restaurant deep fryers, it seems to reason, are put to far greater use than household fryers or skillets. In addition, restaurants simply cannot afford to provide oil that has degraded to the point that it is no longer edible. Bad reviews and fewer customers are the results of serving subpar cuisine.

In a study evaluating the frequency that fast food restaurants change oil used for frying, it was found that the majority of fast food restaurants replaced their discarded oil completely with fresh oil twice a week (54%). 8% of the restaurants admitted they changes the oil daily and 10% changed only once a week (6).

Be aware that restaurants will (ideally) do oil changes more often than the average household.

Having more than one deep fryer in a restaurant is something else to consider. This means that some are only for meats and fish, while others are solely for veggies. In this way, they may restrict the kind of meals that break down frying oil quicker to a single fryer, rather than using all of their fryers.

Other factors to think about are:

·         Don’t top up your oil; instead, replace it when it has to be replaced entirely.

·         After the food has come out of the frying, season it with salt.

·         Lower the temperature of the fryer to around 375°.

·         Every three months, give the fryer a thorough cleaning.

While we’re on the subject of frying, you may be perplexed if you like French fries but would rather save time and effort by purchasing frozen packages instead of cutting your own.

Other FAQs about Oils that you may be interested in.

Can you make a cake with olive oil?

How to counteract too much oil in food? 

What is bulletproof MCT oil?

Can I use vegetable oil in a deep fryer?


In this brief guide, we answered the query, “How Often Should You Change the Oil in a Deep Fryer?” and discussed how many times oil can be reused in the deep fryer?


  1. Sun, Yangbo, et al. Association of fried food consumption with all cause, cardiovascular, and cancer mortality: prospective cohort study. bmj, 2019, 364. 
  2. Kaur, Amarbir, et al. Changes in chemical properties and oxidative stability of refined vegetable oils during short‐term deep‐frying cycles. J Food Process Preserv, 2020, 44, e14445.  
  3. Çağlar, Abdullah, Erman Duman, and Mehmet Musa Özcan. Effects on edibility of reused frying oils in the catering industry. Int J Food Prop, 2012, 15 69-80.
  4. Lee, Jookyeong, et al. Chemosensory device assisted-estimation of the quality of edible oils with repetitive frying. Foods, 2021, 10, 972.
  5. Bordin, Keliani, et al. Changes in food caused by deep fat frying-A review. Archiv latinoam  nutr, 2013, 63, 5-13.
  6. Esfarjani, Fatemeh, et al. Evaluating the rancidity and quality of discarded oils in fast food restaurants. Food sci nutr, 2019, 7, 2302-2311.

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