You’re Probably Throwing Away Frying Oil Way Too Soon

Deep-frying at home gets a bad rap, mainly because it’s thought of as inconvenient and wasteful. Fears of grease-stained walls and lingering oil odors scare many off, and then there’s all that oil.

But deep-frying deserves a place in the home cook’s repertoire—nothing beats freshly fried onion rings or chicken cutlets, and it doesn’t get fresher than straight out of the fryer and into your mouth (after a few beats to cool, of course). If you plan on deep-frying at home, however, it’s crucial to understand how—and how long—you can store and reuse oil. Reusing oil isn’t just OK; it’s a smart way to save money and reduce waste, as long as you treat that glossy, golden oil with care. (Kenji’s written a highly detailed article about reusing oil, so check it out if you haven’t already.) 

With the right oil, steady temperature control, and a few cleaning tips, you can keep it fresh for longer while enjoying crispy fried foods with no regrets.

Choose Oil Wisely

Certain oils are better suited for frying than others, and selecting the right kind is the first step in ensuring fry-oil longevity. Mildly flavored oils with high smoke points (the temperature at which smoke appears on the oil’s surface) are the most common and versatile choice. We generally recommend selecting an oil with a smoke point above 400°F (205°C), which includes peanut oil, corn oil, canola oil, grapeseed oil, and avocado oil, among others (though there is a case to be made for frying in olive oil if you can stomach the cost). Many of those options are relatively affordable, which is a good thing when you’re buying a lot of it.

Watch the Oil Temperature

Preparing your oil for the long road begins before your first fry. Given enough time and exposure to heat, light, and air, oil will decompose, and that breakdown will happen even faster if you exceed the oil’s smoke point. Hitting that smoke point also lowers it, making it harder to reuse the oil in the future.

You can actually smell and taste the effects of overheating oil, as fatty molecules degrade and release a chemical called acrolein, which has a harsh and bitter flavor. Oils that are heated above their smoke point also begin to release fishy-smelling vapors, even if there’s no seafood being fried.

To prevent this, it’s crucial to keep a watchful eye on the oil’s temperature whenever frying, and control the heat throughout.

Clean the Oil Well (Including During Frying)

Oil cleanliness also plays a huge role in its longevity. The math is simple: The more particles left over in your oil, the faster it will break down. Tiny bits of batter and breadcrumbs left behind in the oil continue to fry every time you reheat it. With every additional fry, these particles eventually burn, releasing acrolein and other polymeric compounds that accelerate the oil’s breakdown and oxidation, leading to rancid flavors, darkening, and smoking at lower temperatures. The fix? Clean your oil well, and you’ll likely be able to use it several times.

Koichi Endo, who specializes in the art of deep-frying at the Michelin-starred New York restaurant Tempura Matsui, recommends patting the ingredients dry before frying (a good idea anyway to avoid spatter from water hitting hot oil) and avoiding an overly heavy or poorly applied dredge that’s more likely to slough off. The amount of particles, of course, will change depending on the coating applied. Battered foods, such as tempura or Korean fried chicken, will leave behind fewer impurities than breaded or flour-dredged foods, such as chicken cutlets. 

To avoid a build up of crumbs in the oil, it’s also a good idea to clean out food particles as you fry, which will further prolong the oil’s life: Using a fine-mesh strainer, gently swirl the oil in one direction, then flip the spider and move it the opposite way (into the current) to catch stray bits. After frying, let the oil cool to room temperature, then use a fine-mesh strainer lined with cheesecloth or paper towels to strain out any remaining debris. 

How to Store Oil Between Frying Sessions

Transfer the cleaned oil to a resealable airtight vessel or a saved oil jug, screw on the lid, and place it in a cool, dark space such as the fridge for several months or until signs of deterioration appear. If your fridge has limited space, storing it in the pantry is also perfectly suitable.

For long-term storage, the freezer is a great option if you have the space; the below-freezing temperatures slow oxidation dramatically and can significantly extend the shelf life. Just be sure to label it clearly and let it thaw completely at room temperature before use. Avoid storing oil near the stove, since heat will accelerate rancidity. Whenever you want to reuse the oil, simply add it to your pot and reheat to the frying temperature.

Keeping old oil around is a good idea for future fry sessions, too: Adding a bit of used oil to a fresh batch can actually improve browning. As oil breaks down, it becomes less hydrophobic, meaning it interacts more readily with water. In the short term, this helps the oil make better contact with moisture-laden foods, promoting more efficient frying and better browning. However, if the oil becomes too broken down, and therefore no longer hydrophobic, it can lose its ability to repel water entirely, causing food to absorb excess oil and turn soggy instead of crisp.

A Warning on Reusing Oil

Clearly, reusing oil is a good, economical practice. However, it’s best to avoid reusing frying oil if you’ve fried something with a strong odor in it, especially if you’re frying a different type of food. For example, oil that’s been used to fry chicken or fish should not be used to fry pastries and sweets such as doughnuts, churros, and funnel cakes, as oil can retain the flavors of foods and then impart them to the next batch of food you fry in it. (Who wants to eat a fish-flavored doughnut? Not us!)

When and How to Discard Old Oil

So you’ve fired up the deep fryer with the same batch of oil multiple times, produced some beautiful fritto misto and jalapeño poppers, and cleaned up your mess—all except for the leftover frying oil. How do you know if it’s still good to keep for your next frying session, or whether it’s time to toss it? And how should you get rid of it when it is time to part ways?

First, check to see if the oil appears dark or sticky, exhibits steam bubbles (a sign of moisture in the oil known as foaming), or has a rancid smell. If it checks any of the above boxes, it’s best to dispose of it. Even if the oil passes the visual and smell checks with flying colors after a dozen or so uses, it’s best to toss the oil and start with a fresh batch.

Whatever you do, do not pour it down the drain. Instead, transfer the oil to a resealable container and discard with your regular trash, or use a solidifying agent such as gelatin or “waste cooking oil powder” for mess-free disposal. (You can read more about it in our guide to oil disposal here.)