Articles · Cooking
Which oil should you fry with?
Smoke points, stable fats and a few myths: how to pick an oil for the pan, the wok and the deep fryer, and when olive oil is perfectly fine.
· 6 min read
Stand in front of the supermarket shelf and count the bottles: olive, extra virgin olive, rapeseed, sunflower, peanut, avocado, coconut, "light", "pure", "for frying". Do you really need a different oil for every job? And is it true that you should never fry with olive oil?
The short answer: most everyday frying works with two or three oils, and olive oil is not the villain it's made out to be. The long answer is more interesting, so let's heat the pan.
What actually happens to oil in a hot pan?
Oil is mostly made of fats called triglycerides. Heat, air and water from the food slowly break them apart and react with them. Some of what forms is harmless, some gives fried food its lovely smell, and some you would rather not eat or breathe in, especially when an oil is pushed too hot or used again and again.
Two things decide how well an oil copes:
- Its smoke point: the temperature at which it starts to smoke steadily. Past it, the oil breaks down fast.
- Its stability: how easily its fats react with oxygen when heated. This depends mostly on what kind of fat it is, and on the antioxidants it carries.
Think about it: Which bottle is by your stove right now, and do you know if it's refined or not?
Smoke point: useful, but not the whole story
Refining removes the bits of fruit or seed, free fatty acids and other small parts that start smoking early, so refined oils usually smoke at higher temperatures than unrefined ones. Rough figures, which vary from brand to brand:
- Butter: about 150–175 °C (the milk solids burn first). Ghee, with them removed, copes with far more.
- Extra virgin olive oil: about 190–210 °C.
- Refined ("light") olive oil, refined rapeseed and refined sunflower oil: roughly 220–240 °C.
- Refined peanut oil: about 230 °C. Refined avocado oil: about 250 °C or more.
Most pan frying happens between about 160 and 190 °C, and deep frying at 160–180 °C. A searing-hot wok can go past 200 °C.
So is extra virgin olive oil too delicate to fry with? Not for ordinary pan frying. Its smoke point is above the temperatures most frying needs, and it has another strength that the smoke point doesn't show.
Stability: the kind of fat matters
Fats come in three broad kinds: saturated, monounsaturated and polyunsaturated. The more unsaturated a fat is, the more easily it reacts with oxygen when heated.
- Monounsaturated-rich oils (olive, rapeseed, and "high-oleic" sunflower or safflower) hold up well to heat.
- Polyunsaturated-rich oils (regular sunflower, corn, soybean) break down faster when heated for a long time, and lab studies find they form more aldehydes, reactive compounds you would rather not eat or breathe in.
- Saturated fats (coconut oil, butter, lard) are very stable, but eating less saturated fat is one of the best-supported pieces of heart-health advice.
Extra virgin olive oil also carries natural antioxidants. In one deep-frying study, olive oils lasted 24–27 hours of frying before reaching the legal limit for broken-down oil, against 15 hours for a vegetable-oil blend, and a review of frying studies found olive oil usually does as well as refined seed oils, or better.
An Old Woman Cooking Eggs, Diego Velázquez, 1618, Scottish National Gallery, Edinburgh. Eggs cooking in a glazed pot of hot oil over embers, four hundred years ago. What do you think was in that pot? In Seville, where Velázquez painted it, olive oil is a good guess. Public domain · Wikimedia CommonsSo which oil for which job?
Here's a simple way to stock the kitchen:
- Everyday frying and roasting: olive oil (extra virgin or refined) or rapeseed oil. Both are rich in monounsaturated fat and cope well.
- Very hot cooking (searing, a smoking wok): a refined oil with a high smoke point, such as refined peanut, rapeseed or avocado oil, or "light" olive oil.
- Deep frying: refined high-oleic sunflower, refined rapeseed or peanut oil, at 160–180 °C, with a thermometer if you have one.
- Flavour at the end: extra virgin olive oil, toasted sesame oil or butter, added off the heat or at low heat.
Coconut oil and butter are stable, but they are mostly saturated fat. The World Health Organization advises keeping saturated fat under a tenth of the day's energy, so use them for flavour, not as the everyday oil.
Try this: Heat the pan first, then the oil, and add the food as soon as the oil shimmers. If you see steady smoke, the pan is too hot: take it off the heat, let it cool and start again.
Can you reuse frying oil?
A little, yes, but not endlessly. Every heating breaks the oil down further, and the breakdown speeds up as it goes. Strain used oil, keep it cool, dark and covered, and throw it away when it:
- smokes at a lower heat than it used to,
- turns dark and thick, or foams,
- smells sharp, fishy or stale.
Think about it: How many times has the oil in your deep fryer been used? If you can't remember, it may be time for fresh oil.
Quick quiz
Does a higher smoke point always mean a better frying oil?
No. It helps, but how stable an oil's fats are matters too. Olive and rapeseed oils hold up well in frying, even though some seed oils smoke at higher temperatures.
Refined peanut oil or butter for a very hot wok?
Refined peanut oil. Butter's milk solids burn at a much lower temperature.
Is it fine to reuse frying oil again and again?
Not endlessly. Each heating breaks it down further. Strain it, store it cool and dark, and replace it once it darkens, foams, smells sharp or smokes early.
Sources
General information, not medical advice. If you have a health condition, are pregnant or take medication, ask a doctor or dietitian what is right for you.