Which cooking oil to choose? Ranking and comparison of oils by thermal stability

For frying – both in a pan and deep-frying – oils with high oxidative stability are best: refined rapeseed oil and avocado oil for daily use, and coconut oil, ghee, and refined olive oil for frying at higher temperatures or reusing the same fat multiple times. A key caveat here is that the smoke point itself, which we most often consider when buying, doesn't tell us much about how the oil will behave during prolonged frying – its oxidative stability and fatty acid composition tell us more.

In this article, we explain step by step why the smoke point can be a misleading criterion, how saturated, monounsaturated, and polyunsaturated fatty acids behave under heat, and which oils will work best for specific applications – from daily pan-frying to deep-frying and long-term storage. You'll also find a comparative table, a list of oils to avoid when cooking with heat, and practical tips on how to assess whether the oil in your kitchen is still fit for use.

1. What is the best oil for frying?

For frying – both in a pan and deep-frying – oils with high oxidative stability and a predominance of monounsaturated or saturated fats are best: refined rapeseed oil, coconut oil, ghee (clarified butter), refined olive oil, and avocado oil. It is oxidative stability – not just the smoke point – that determines how an oil behaves under prolonged exposure to high temperatures.

When choosing an oil for frying, it's worth considering three criteria simultaneously, not just one, often advertised parameter:

• Smoke point – the temperature at which the oil begins to break down and smoke
• Oxidative stability – resistance to oxidation under prolonged heat, oxygen, and light
• Fatty acid profile – the proportion of saturated, monounsaturated, and polyunsaturated fats

The smoke point is the parameter most often found on labels and in online rankings, but studies on edible oils show that this is an incomplete picture. A review of literature on frying oils defines the smoke point as the temperature at which the oil begins to break down into free fatty acids and glycerol – this is merely a visual signal of degradation beginning, not a measure of how many harmful compounds were formed earlier, during the cooking process itself.

Further in the article, you'll find a complete comparative table with specific values for individual oils and separate chapters dedicated to each popular cooking oil.

2. What is the smoke point and why isn't it the only important factor?

The smoke point is the temperature at which a thin, bluish wisp of smoke begins to rise from the surface of the oil. This indicates that the oil has begun the process of breaking down triglycerides into free fatty acids and glycerol, from which acrolein is then formed – a compound responsible for the irritating smell of burnt fat.

The problem is that the smoke point is measured under laboratory conditions, with a small amount of oil heated in a standardized vessel – this does not reflect the real conditions of frying in a larger quantity of fat, in a pan or deep fryer. Additionally, this value decreases as the frying process continues, especially in oils rich in polyunsaturated fats, such as sunflower, corn, or soybean oil.

2.1. What happens to oil after its smoke point is exceeded?

Once the smoke point is exceeded, the triglycerides in the oil begin to break down into free fatty acids and glycerol. Glycerol further decomposes into acrolein – a volatile compound with a pungent odor, which is the main component of visible smoke. This stage marks the beginning of the deterioration of both the oil's nutritional value and its taste.

Notably, studies on olive oil show that the smoke point itself largely depends on the free fatty acid content of the oil – the higher their content, the lower the smoke point. More highly refined oils usually have fewer free fatty acids, and thus a higher smoke point – but this does not automatically mean they are more stable during prolonged frying.

2.2. Why is oxidative stability more important than the smoke point?

Oxidative stability determines how long an oil resists oxidation under the influence of heat, oxygen, and light before it begins to form harmful breakdown products – peroxides, aldehydes, and polar compounds. These compounds, not the smoke itself, are the main reason why overheated or repeatedly used oils are detrimental to health.

This is best illustrated by a study published in Acta Scientific Nutritional Health, where ten popular cooking oils were heated to 240°C and maintained at 180°C for 6 hours – conditions similar to intensive frying. Extra virgin olive oil, despite a relatively lower smoke point than, for example, rapeseed oil or grapeseed oil, produced the fewest polar compounds among all tested oils. Rapeseed oil, despite a higher smoke point, generated significantly more of these unfavorable compounds.

This difference is primarily due to the fatty acid composition. Double bonds present in monounsaturated and polyunsaturated fats are where the reaction with oxygen most easily occurs – the more such bonds, the faster the oil oxidizes. Saturated fats, devoid of double bonds, are the most resistant in this regard, and monounsaturated fats (dominant in olive oil and avocado oil) occupy an intermediate position – stable enough for most culinary applications, while maintaining a beneficial health profile.

3. Which fatty acids best withstand high temperatures?

How long oil remains stable under heat depends primarily on the number of double bonds in the fatty acid molecules from which it is composed. The more such bonds, the more sites susceptible to oxygen attack – and thus the faster oxidation occurs. Therefore, knowing the distinction between saturated, monounsaturated, and polyunsaturated fatty acids allows us to predict the oil's behavior in the pan much better than the smoke point alone.

3.1. Saturated fats

Saturated fatty acids have no double bonds in their structure – each carbon atom in the chain is fully "saturated" with hydrogen atoms. The absence of double bonds means there are no sites where oxygen could initiate an oxidation reaction. This makes saturated fats the most resistant to thermal degradation among all types of fatty acids.

Oils and fats rich in saturated acids – coconut oil, ghee, lard – maintain high stability even after many heating cycles. This is why traditional cuisines, long before the era of gas chromatography and OSI indicators, relied on animal fats and coconut oil for frying.

From a health perspective, however, the context of the entire diet matters: according to the EFSA-approved health claim (EU Regulation 432/2012), replacing saturated fats in the diet with unsaturated fats contributes to maintaining normal blood cholesterol levels. This statement concerns the overall fat balance in the diet, not a one-time choice of oil for a specific dish – thermal stability and health impact are two separate criteria that should be considered together.

3.2. Monounsaturated fats

Monounsaturated fatty acids (MUFAs), such as oleic acid, which is dominant in olive oil and avocado oil, have one double bond in their chain. This bond represents a potential site for oxidation, but there are significantly fewer of them than in polyunsaturated fats, making MUFAs an intermediate solution – stable enough for most culinary applications, including pan-frying and short deep-frying.

It is precisely the high content of oleic acid, combined with naturally occurring antioxidants in olive oil (polyphenols, tocopherols), that explains why olive oil performs better in comparative studies regarding thermal stability than some oils with a higher smoke point but richer in polyunsaturated fats.

3.3. Polyunsaturated fats – why are they the least stable?

Polyunsaturated fatty acids (PUFAs) – such as linoleic acid (omega-6) or alpha-linolenic acid (omega-3) – have two or more double bonds. Each subsequent bond represents an additional, "weakened" site in the carbon chain where the reaction with oxygen occurs more easily. In practice, this means that the higher the proportion of PUFAs in an oil, the faster peroxides, aldehydes, and other breakdown products are formed under heat – compounds that not only worsen the taste and smell of food but are also detrimental to health with long-term exposure.

For this reason, oils rich in PUFAs – unrefined sunflower oil, grapeseed oil, soybean oil, and especially linseed oil – are not a good choice for frying, even if their smoke point appears favorable on paper. Their place is rather on the plate cold – as an addition to salads or spreads – rather than in a hot pan. We will describe this in more detail in the chapter dedicated to oils best avoided for frying.

4. Ranking: Which frying oil works best?

The table below compares the most commonly chosen oils and fats for frying in terms of three key parameters: approximate smoke point, dominant fatty acids, and oxidative stability. Values may vary slightly between manufacturers, degree of refinement, and production batch – treat them as a reference point, not a strict standard.

Scroll right to see the full table (on mobile devices) →

The comparison clearly shows that the highest smoke point (avocado oil) does not correlate with the highest oxidative stability (extra virgin olive oil and coconut oil) – this confirms what we discussed in Chapter 2. Standard, unrefined sunflower oil and oils rich in polyunsaturated fats were intentionally excluded from this comparison – we will discuss them separately in the chapter dedicated to oils to avoid when frying.

In the next chapter, we will break this down into its constituent parts – you will see how individual types of fatty acids behave under high temperatures and why they, and not the label on the bottle, should determine the choice of oil for frying.

5. Refined Rapeseed Oil – Is It the Best Choice for Everyday Frying?

Refined rapeseed oil is one of the best all-purpose oils for everyday frying – it has a neutral taste, an affordable price, a good smoke point, and a favorable fatty acid profile. However, it is not the most stable oil for long or repeated frying at very high temperatures – in this role, oils with a higher proportion of saturated fats, described in subsequent chapters, will be better.

The fatty acid composition of rapeseed oil is approximately 60–64% monounsaturated fats (mainly oleic acid), 28–30% polyunsaturated fats (with an omega-6 to omega-3 ratio close to 2:1), and only 6–7% saturated fats. This is one of the most favorable fatty acid profiles among popular cooking oils – and also the reason why its oxidative stability is moderate, not the highest: the proportion of polyunsaturated fats is significantly higher than in olive oil or avocado oil.

5.1. What Does Rapeseed Oil Contain Besides Fatty Acids?

Rapeseed oil is also one of the best plant sources of vitamin E and alpha-linolenic acid (ALA) – a plant-based omega-3 fatty acid. According to approved EFSA health claims (EU Regulation 432/2012):

• ALA contributes to the maintenance of normal blood cholesterol levels (condition: the product must be at least a source of ALA, and the effect is achieved with a daily intake of 2 g of ALA)
• Vitamin E contributes to the protection of cells from oxidative stress

5.2. Refined or Cold-Pressed?

Only refined rapeseed oil is suitable for frying. The unrefined (cold-pressed) version has a low smoke point and an intense, nutty flavor that quickly deteriorates under high temperatures – its place is in salads, spreads, or as a cold addition to ready meals, not in a frying pan. Refining slightly reduces the content of vitamin E and free fatty acids, but it is thanks to this process that the oil gains a higher smoke point and greater predictability during frying.

5.3. When to Choose Rapeseed Oil and When to Choose Another?

Refined rapeseed oil works best for:

• everyday pan-frying at moderately high temperatures
• dishes where a neutral taste is desired (it won't dominate the aroma of the dish)
• occasional frying, without repeated reuse of the same oil

If you fry frequently at very high temperatures, repeatedly reuse the same oil, or prepare large-scale deep-frying, an oil with higher oxidative stability – coconut, ghee, or avocado oil – will be a better choice.

6. Coconut Oil – Is It Suitable for Frying?

From a purely technical standpoint, coconut oil is one of the most stable oils for frying – its high saturated fat content means it withstands prolonged and repeated heating very well, virtually without forming harmful oxidation products. However, the health aspect is more complex: due to its high saturated fat content, major cardiology organizations recommend limiting its intake, despite its good thermal stability.

6.1. Composition of Coconut Oil and Its Thermal Stability

Coconut oil consists of approximately 82–90% saturated fats, almost half of which is lauric acid – a medium-chain fat. The absence of double bonds in the structure of these fatty acids means minimal susceptibility to oxidation, even with many hours of frying at high temperatures. This is why coconut oil is a popular choice for deep-frying and baking that requires a stable fat at higher temperatures.

6.2. What Does Science Say About the Effect of Coconut Oil on Cholesterol?

The American Heart Association (AHA), in its official statement from 2017, recommends limiting coconut oil intake and replacing it with unsaturated fats, citing its high saturated fat content. Meta-analyses of clinical studies comparing coconut oil with vegetable oils (including soybean, olive oil, and safflower oil) showed that its consumption raises both total cholesterol and LDL fraction, with a slight increase in HDL fraction. Similar conclusions were presented in a 2024 systematic review by the World Health Organization (WHO), which indicated an unfavorable effect of coconut oil on lipid parameters compared to other vegetable oils.

However, lauric acid, dominant in coconut oil, introduces some ambiguity, as it raises LDL cholesterol levels to a lesser extent than palmitic or myristic acid, while at the same time raising "good" HDL cholesterol levels more significantly than other saturated fats. Nevertheless, this does not change the general conclusion of major scientific societies – coconut oil, despite its culinary stability, should not be the main fat in a daily diet, and its use should be treated as part of a broader, varied diet dominated by unsaturated fats.

Organic Odorless Coconut Oil 1 L - Batom

6.3. Refined or Virgin Coconut Oil?

Refined coconut oil has a neutral taste and a higher smoke point (approx. 230°C), making it a better choice for frying dishes where a discernible coconut note is not desired. Virgin (unrefined) coconut oil retains a distinct coconut aroma and a slightly lower smoke point – it will be better suited for Asian cuisine or baked goods where this flavor is desired, and for frying at moderate temperatures.

7. Olive Oil – Refined vs. Extra Virgin, Can You Fry with It?

Yes, you can fry with olive oil – both refined and extra virgin. It's one of the most widespread culinary myths that olive oil "is not suitable" for hot cooking. In practice, as we showed in Chapter 2, extra virgin olive oil showed one of the highest oxidative stabilities among all tested oils in comparative studies – despite a relatively lower smoke point than refined oils.

7.1. What's the Difference Between Refined and Extra Virgin Olive Oil?

Extra virgin olive oil (first press) is produced solely by mechanical means, without the use of solvents or high temperatures, thus preserving most of the polyphenols, chlorophyll, and vitamin E, as well as its characteristic, distinct flavor.

Refined olive oil undergoes an additional purification process that removes free fatty acids and some flavor compounds, but also raises the smoke point and extends the product's shelf life.

In practice, this means a compromise: refined olive oil will withstand very high temperatures better, but loses some of the nutritional and taste qualities that are the strong suit of the extra virgin version.

7.2. Is Extra Virgin Olive Oil Suitable for Frying?

Yes – and not just for quick sautéing. A study comparing ten popular cooking oils under thermal stress (heating to 240°C and maintaining at 180°C for 6 hours) showed that extra virgin olive oil generated the fewest polar compounds among all tested oils – less than refined olive oil and significantly less than rapeseed or grapeseed oil, despite their higher smoke points. This resistance is due to the combination of a high content of oleic acid (monounsaturated fat) with naturally occurring antioxidants in olive oil – polyphenols and tocopherols (vitamin E), which protect the oil from oxidation even during heating itself.

In practice, this means that extra virgin olive oil works well for pan-frying and short deep-frying at typical home temperatures. For very long, hours-long deep-frying at extremely high temperatures (significantly above its smoke point), however, refined olive oil or another oil with a higher smoke point, as described in Chapter 4, would be a better choice.

Organic Extra Virgin Olive Oil 750 ml - Vilgain

7.3. Polyphenols in Olive Oil – When Can a Health Claim Be Made?

According to EU Regulation 432/2012, olive oil can carry the health claim: "olive oil polyphenols contribute to the protection of blood lipids from oxidative stress." However, the condition is specific – the olive oil must contain at least 5 mg of hydroxytyrosol and its derivatives per 20 g of product, and the effect applies to a daily intake of 20 g of olive oil. This level of polyphenols is found primarily in good quality extra virgin olive oils – in refined olive oil, most of these compounds are removed during the refining process, so this claim practically does not apply to it.

8. Ghee and Clarified Butter – Traditional Fat for Frying

Ghee (clarified butter) is a fat with high thermal stability, produced by slowly heating butter and separating pure fat from water and milk proteins (casein and whey). The result is a product with a significantly higher smoke point than regular butter, a nutty flavor, and a long shelf life without needing refrigeration.

8.1. How Does Ghee Differ from Regular Butter?

Regular butter contains, in addition to fat, water and a small amount of milk proteins and lactose, which quickly burn at high temperatures – this is why butter smokes and darkens at moderate temperatures (approx. 150°C). The clarification process removes these components, raising ghee's smoke point to around 250°C. In practice, this means that ghee retains a buttery flavor but withstands much higher temperatures than butter – and for this reason, it is well suited for frying, while regular butter is better for dishes prepared at lower temperatures or as an addition at the end of cooking.

Due to the removal of casein and most lactose, ghee is usually well tolerated by people with lactose intolerance – however, the product still comes from milk, so people with milk protein allergies should exercise caution and consult a doctor.

8.2. Composition and Nutritional Value of Ghee

Ghee is almost pure fat – approx. 99% fat, most of which are saturated acids, and the rest monounsaturated fats. Thanks to its low content of polyunsaturated fats, ghee, like coconut oil, is resistant to oxidation at high temperatures. It also contains fat-soluble vitamins A, D, E, and K, and their concentration depends, among other things, on the diet of the cows from which the milk comes.

Ghee also contains small amounts of butyric acid (butyrate) and conjugated linoleic acid (CLA) – compounds characteristic of ruminant fat, whose potential health effects are under research, but at the current stage there is no basis for formulating unambiguous health claims about them.

Clarified Butter Ghee 240 g - Pięć Przemian

8.3. What Is Ghee Best Used for in the Kitchen?

Ghee works particularly well for:

• pan-frying at high temperatures (e.g., searing meat, vegetables)
• short, intense frying requiring a distinct, buttery flavor
• Indian and Middle Eastern dishes, where it traditionally serves as a staple cooking fat

For long, hours-long deep-frying on a large scale, coconut oil or avocado oil would be a better, more economical choice – ghee, due to its higher price and intense flavor, works best as a fat for specific dishes, not as an all-purpose deep-fryer fat.

9. Avocado Oil – High Stability, Higher Price

Avocado oil is one of the most versatile oils for frying at very high temperatures – it has the highest smoke point among popular cooking oils, good oxidative stability, and a neutral taste. Its main limitation is not quality, but price and a significant problem with product counterfeiting on the market, which is worth knowing before purchasing.

9.1. Composition and Thermal Stability

Avocado oil (refined) reaches a smoke point of 250–270°C, making it one of the best choices for frying at extremely high temperatures and short searing in very hot fat.

Its fatty acid profile – a dominance of monounsaturated oleic acid with a relatively small proportion of polyunsaturated fats (approx. 12–14%) – ensures good oxidative stability, similar to olive oil, although usually slightly lower than in extra virgin olive oil or coconut oil, which contain no or almost no polyunsaturated fats.

9.2. Quality Problem – Why Is It Worth Carefully Choosing a Brand?

The growing popularity of avocado oil has made this market particularly susceptible to product counterfeiting. A study conducted by researchers from the University of California, Davis, showed that as many as 82% of tested avocado oil samples available on the American market were either rancid before their expiration date or mixed with other, cheaper oils (most commonly soybean, sunflower, or grapeseed oil) without proper information on the label.

Another UC Davis study from 2024, covering private label products, confirmed this problem, indicating a low percentage of samples meeting purity standards in terms of fatty acid profile and vitamin E content.

Avocado Oil Spray 200 ml - Vilgain

9.3. When is it worth reaching for avocado oil?

Avocado oil is best for high-temperature frying – quick searing of meat on a very hot pan, stir-frying in a wok, or deep-frying requiring temperatures above 220–230°C.

Due to its higher price than most oils described in this article, it doesn't have to be a fat used daily for everything – it works better as a specialized choice for specific applications where its high smoke point truly matters.

10. Which oils to avoid when frying and why?

Not every oil available on the store shelf is suitable for hot cooking. As we showed in section 3.3, the higher the proportion of polyunsaturated fats in the oil, the faster it oxidizes under high temperatures – regardless of its smoke point listed on the label.

10.1. Linseed oil and walnut oil

Linseed oil has one of the lowest smoke points among edible oils (approx. 107°C) and is exceptionally rich in alpha-linolenic acid – the most prone to oxidation among commonly consumed fatty acids. Heating linseed oil destroys its nutritional value and leads to the formation of undesirable breakdown products much faster than with other oils.

The same applies to walnut oil, which – despite its intense, desirable flavor in cold dishes – has a low smoke point and high content of polyunsaturated fats.

Both these oils are best suited as an addition to salads, spreads, or ready-to-eat cold dishes, added just before serving.

10.2. Unrefined sunflower oil

Standard, unrefined sunflower oil (other than the high-oleic variety described in section 4) has a low smoke point and a high proportion of linoleic acid – a polyunsaturated fat that oxidizes quickly when heated.

Only refined high-oleic sunflower oil, clearly marked on the label, is better for frying – it has a completely different, much more favorable fatty acid profile than the standard version.

10.3. Grapeseed oil – the trap of a high smoke point

Grapeseed oil is a good example of the mechanism described in section 2 – its smoke point is relatively high (approx. 200–216°C), which gives the impression that it is suitable for frying. The problem is that it consists mostly (up to 70%) of linoleic acid – a polyunsaturated fat with low oxidative stability.

In comparative studies described in section 2.2, grapeseed oil was among the oils that generated the most polar compounds during prolonged heating, despite its high smoke point. This is one of the best examples of why the smoke point alone can be a misleading selection criterion.

10.4. General rule: beware of repeatedly used oil

Regardless of the oil type, repeated heating and reuse of the same fat for frying leads to the accumulation of polar compounds and free fatty acids, reducing both the quality and safety of the oil – even if it was initially an oil with high stability.

Signs that the oil is only fit for disposal include noticeable darkening, thickening, abundant foaming during frying, and an unpleasant, rancid smell. Ways to independently assess the degree of oil wear will be described in more detail later in the article.

11. Pan-frying vs. deep-frying – is a different oil needed?

Not always – many of the oils described in this article will work for both methods. However, the difference lies in how long and in what volume the oil is exposed to high temperatures, which directly affects how quickly it loses its stability.

11.1. How does the thermal load on oil differ in both methods?

Pan-frying typically occurs in a thin layer of oil, in a shorter time, and at a temperature rarely exceeding 160–180°C. Deep-frying requires a much larger volume of oil, longer exposure time to heat, and often a higher, more stable temperature (typically 170–190°C), and the oil itself is usually used repeatedly for subsequent batches of food.

It is precisely the repeated heating – not just the temperature – that puts the most strain on the oil during deep-frying: each subsequent heating cycle accumulates free fatty acids and polar compounds, which we discussed in sections 2 and 10.4.

11.2. Which oil to choose for which method?

For pan-frying, where the oil is used once or for a short period, a wider range of oils will work well – rapeseed, olive oil (refined and extra virgin), avocado oil, or ghee. The main factors here are the smoke point suitable for the dish's temperature and the preferred flavor.

For deep-frying, especially when the oil is to be used repeatedly, oils with the highest oxidative stability are better: coconut oil, avocado oil, ghee, or refined olive oil. The higher the oil's resistance to oxidation, the more frying cycles it can endure before losing quality.

12. How to store oil to keep it fresh longer and prevent rancidity?

Three factors accelerate oil rancidity the most: light, heat, and oxygen. Proper storage – regardless of the type of oil – can extend its shelf life by many months, while poor storage can spoil even the highest quality oil within a few weeks.

12.1. Light, heat, and oxygen – three main enemies of oil's shelf life

• Light – especially UV radiation, accelerates oxidation reactions. That's why the highest quality oils are sold in dark glass or opaque packaging.
• Heat – keeping an oil bottle next to the stove or oven, though convenient, significantly shortens its shelf life. The optimal storage temperature is cool, stable conditions, preferably below 20°C.
• Oxygen – each time the bottle is opened, air enters, initiating oxidation. A tight, securely closed cap limits this process.

12.2. Practical storage rules

• Store oil in a dark cabinet or drawer, away from the stove, oven, and window.
• Always close the cap tightly after use.
• Buy smaller packages of oils you use rarely, so you don't keep an open bottle for months.
• Oils particularly rich in polyunsaturated fats (e.g., flaxseed, walnut) are best stored in the refrigerator after opening.
• Cloudiness in oil stored in the refrigerator (e.g., olive oil) is a normal phenomenon related to low temperature, not a sign of spoilage – after warming to room temperature, the oil regains clarity.

Oils rich in saturated fats (coconut, ghee) are naturally more resistant to rancidity and can be stored at room temperature much longer than oils rich in polyunsaturated fats – this is another practical consequence of the mechanism described in section 3.

13. How to assess oil quality yourself after opening?

You don't need a laboratory to notice that oil has lost its quality – a few simple sensory cues allow you to assess this in your home kitchen, both for a freshly opened bottle and for oil used repeatedly for frying.

13.1. What to look for in a freshly opened bottle?

• Smell – should be neutral or characteristic of the oil (e.g., slightly nutty for olive oil), without a sharp, "paint-like" note.
• Taste – no bitter, soapy, or "waxy" aftertaste.
• Color and clarity – no noticeable sediment or cloudiness unrelated to low storage temperature.

13.2. How to recognize that oil used for frying is only fit for disposal?

During subsequent frying cycles, oil gradually degrades – it's worth observing a few signs that suggest it should not be reused:

• noticeable darkening compared to the initial color.
• thicker, stickier consistency.
• abundant, persistent foaming during frying (instead of a short sizzle).
• smoke appearing at a distinctly lower temperature than at the beginning of oil use.
• unpleasant, rancid smell, even after cooling.

If you notice at least two of these signs simultaneously, it is safest to replace the oil with fresh, regardless of how many times it has been used before.

13.3. When is it worth opting for a more precise quality assessment?

The above sensory methods work well in everyday cooking, but they do not allow for a precise determination of the degree of oil oxidation – especially when purchasing a finished product, where we have no reference point before opening.

If you want to learn how to professionally assess oil quality before purchase and what the Totox index is, check out our separate article: Totox index – how to check oil quality before you buy it?

14. Frequently Asked Questions About Frying Oils

14.1. Can different oils be mixed together when frying?

Yes, mixing, for example, rapeseed oil with a more stable oil (e.g., coconut or avocado) is practiced to combine a lower price with better resistance to high temperatures. However, the stability of such a mixture will be similar to that of the less stable component – it is not possible to "average" oxidation resistance in a simple, linear way.

14.2. How many times can the same oil be safely used for frying?

There is no single universal number – it depends on the type of oil, frying temperature, and the type of food being fried (breading or high water content in the product accelerates oil degradation).

In home conditions, highly stable oils (coconut, avocado, ghee) can usually be used several times, provided they are strained after each use and stored according to the rules in section 12.

If you notice any of the signs described in section 13.2, discontinue reuse regardless of the number of previous cycles.

14.3. Does freezing oil extend its shelf life?

Yes, low temperatures slow down oxidation reactions, so freezing (like refrigeration) can extend the shelf life of oil, especially oil rich in polyunsaturated fats. After thawing, the oil may be temporarily cloudy or partially solidified – this is normal and does not indicate a loss of quality; simply wait until it returns to room temperature.

14.4. Does a higher oil price always mean better quality?

Not necessarily. As we showed with the example of avocado oil in section 9.2, a high price does not guarantee authenticity or absence of product adulteration. A better indicator of quality than the price itself is the pressing or production date, storage method in the store (protection from light), and – if the manufacturer provides them – laboratory analysis results.

14.5. Can cold-pressed rapeseed oil be gently heated, e.g., for short simmering?

Brief heating at low temperatures (e.g., gently simmering vegetables) usually will not drastically damage the oil, but it will also not utilize its main nutritional benefits. With longer or more intense heating, this oil will lose significantly more value than its refined counterpart. If you plan any frying or prolonged heating, the refined version remains a better choice.

14.6. Is frying in oil inherently less healthy than steaming or baking?

Frying typically involves a higher amount of fat consumed and a higher caloric content of the dish than steaming or baking without added fat, which should be considered when planning an overall diet. However, choosing an appropriate, stable oil and avoiding overheating or repeated use significantly limits the formation of unfavorable compounds mentioned in this article.

15. Summary

Choosing a good frying oil is practically an equation of three variables: smoke point, oxidative stability, and fatty acid profile – rather than focusing solely on the first, most commonly advertised parameter. An oil with an impressive smoke point but rich in polyunsaturated fats (like grapeseed oil or standard sunflower oil) may turn out to be a worse choice than extra virgin olive oil, which has a lower smoke point but significantly higher oxidation resistance.

For everyday pan-frying, a wide range of oils will work well – refined rapeseed, olive oil (refined and extra virgin), or ghee. For intensive, repeated high-temperature frying, it's worth reaching for oils with the highest stability – coconut or avocado oil, while also remembering to moderate the intake of saturated fats in the context of the overall diet.

Regardless of the chosen oil, its durability and safety of use also depend on proper storage and the ability to recognize signs indicating a loss of quality.

16. Sources

1. De Alzaa F., Guillaume C., Ravetti L. (2018). Evaluation of Chemical and Physical Changes in Different Commercial Oils during Heating. Acta Scientific Nutritional Health, 2(6). actascientific.com/ASNH/pdf/ASNH-02-0083.pdf
2. A review of different frying oils and oleogels as alternative frying media for fat-uptake reduction in deep-fat fried foods. sciencedirect.com/science/article/pii/S240584402308708X
3. Deciphering the Complexity of Smoke Point in Virgin Olive Oils to Develop Simple Predictive Models. pmc.ncbi.nlm.nih.gov/articles/PMC12692607
4. Coconut Oil. The Nutrition Source, Harvard T.H. Chan School of Public Health. nutritionsource.hsph.harvard.edu/food-features/coconut-oil
5. Neelakantan N. et al. (2020). The Effect of Coconut Oil Consumption on Cardiovascular Risk Factors. Circulation, American Heart Association Journals. ahajournals.org/doi/10.1161/CIRCULATIONAHA.119.043052
6. Purity and quality of private labelled avocado oil. sciencedirect.com/science/article/pii/S0956713523002372