The last batch of kuttu pakode is out, and there is still half a kadhai of oil left. It looks fine, so you strain it into a steel dabba for tomorrow's puris. It is such a common habit that ICMR-NIN itself calls reusing oil very common, both at homes and in commercial establishments. And the festive season, from Navratri all the way to Diwali, is when the kadhai works hardest.
So can you reuse cooking oil after frying? Here is the short answer from India's own food authorities:
- Avoid frying with the same oil again. Both ICMR-NIN and FSSAI say this.
- At home, you can filter oil used once for frying and use it for cooking curry, but finish it within a day or two.
- Never top up used oil with fresh oil, and throw it out when it smokes, foams, turns dark or changes consistency.
Can you reuse cooking oil after frying?
Not for more frying, ideally. ICMR-NIN's 2024 dietary guidelines say that at household level, oil once used for frying should be filtered and may be used for curry preparation, but using the same oil for frying again should be avoided. That used oil should be eaten within a day or two, and not stored for long.
FSSAI's guidance for households says almost exactly the same thing. Its guidance note on handling used cooking oil suggests filtering once-used frying oil for curries "in order to make it economical", and avoiding using it for frying again.
So the practical rule is simple. Fry once. If there is oil left, strain it and use it up in your sabzi or dal tadka over the next day or two. Do not keep a dabba of old frying oil going for weeks.
Why is reusing cooking oil dangerous?
Oil breaks down when it is used for frying. ICMR-NIN explains that repeated heating of vegetable oils leads to oxidation of their polyunsaturated fats, which creates harmful compounds that may increase the risk of cardiovascular disease and cancer.
FSSAI looks at it through a measure called Total Polar Compounds, or TPC, which build up in oil with repeated frying. FSSAI has fixed a TPC limit of 25%, beyond which vegetable oil shall not be used, and food businesses have had to monitor their frying oil since 1 July 2018. Its guidance note adds that reports have related these compounds to conditions such as high blood pressure, atherosclerosis, Alzheimer's disease and liver disease.
Most of us have no way to measure TPC at home. That is exactly why the home advice is to avoid frying with the same oil again, rather than guess how far gone it is.
How many times can you reuse frying oil?
You may have heard "three times". That number does come from FSSAI, but it is a rule for food businesses, and even there it is a ceiling, not a target.
One more rule is worth sticking on your fridge. ICMR-NIN says used oils should not be mixed with fresh oils and reused. Topping up last week's kadhai with a fresh pour is the habit to drop first.
The same check applies when you buy. A halwai's notice board should tell you whether sweets are made in ghee, oil or vanaspati, as we explained in our guide on how to check fake khoya and mithai.
How do you know cooking oil has gone bad?
FSSAI lists clear signs that oil quality has deteriorated and it should be thrown out:
- Blue-grey smoke appears when you heat it.
- A tough foam forms on top while frying.
- The oil turns dark and murky.
- Its consistency changes from what fresh oil is like.
If you see any of these, stop. Do not strain it and save it for curry either. It is done.
What should you do with leftover frying oil?
Here is a simple routine for the festive season. The first two steps are basic kitchen sense; the rest come from FSSAI's household guidance and ICMR-NIN:
- Let it cool completely before you move it.
- Strain out the bits of food through a fine strainer or a clean cotton cloth.
- Keep it in a separate container. FSSAI specifically says not to pour used oil back into your fresh oil bottle.
- Use it for curries and tadka within a day or two.
- To throw out a small amount, mix it with sand, sawdust, a used towel, paper towels or food scraps, and put it in the dustbin.
- Never pour it down the sink or drain. FSSAI notes that used oil blocks sewers and drains.
For larger amounts, FSSAI runs RUCO (Repurpose Used Cooking Oil), a system that collects used cooking oil from food businesses and turns it into biodiesel.
Easy ways to use less frying oil this festive season
- Fry in smaller batches in a smaller kadhai, so there is less oil left over to tempt you.
- For potato snacks, try an air fryer. ICMR-NIN notes that air frying significantly reduces the oil absorbed compared with deep frying, and can be particularly helpful for starchy foods like potatoes.
- Go easy on packaged namkeen and chips too. Many of them sit in the ultra-processed group, as our ultra-processed foods list for India explains.
- If festive frying is throwing off your plans, our calorie deficit calculator helps you see where you stand.
Frequently asked questions
Can you reuse cooking oil after deep frying?
Not for more deep frying, ideally. ICMR-NIN and FSSAI both say to filter oil used once for frying and use it for curries within a day or two, instead of frying with it again.
How long can you store used cooking oil?
Only a day or two. Both ICMR-NIN and FSSAI say used oil should not be stored for long because it deteriorates faster than fresh oil.
Can you mix used oil with fresh oil?
No. ICMR-NIN says used oils should not be mixed with fresh oils and reused, and FSSAI says not to refill your fresh oil container with used oil.
How do you dispose of used cooking oil at home?
Let it cool, mix it with an absorbent like sand, sawdust or paper towels, and throw it in the dustbin. Do not pour it down the drain.
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This article is general information, not medical advice.
