Let’s talk about spoilage, shelf life, and storing cooking oils.
Say you got a bottle of cooking oil that’s a few months past its date, and you’re thinking: does cooking oil go bad?
Or you simply want to know how long your cooking oil should last after opening the bottle.
Sounds familiar? If so, you’re in the right place.
But before we get to the details, let’s quickly cover what cooking oil actually is so that we’re all on the same page here.
“Cooking oil” and “vegetable oil” are terms used synonymously and, in almost all cases, mean the same thing. If you’ve read my article on the spoilage of vegetable oils, there’s no need to read this one. The information outlined in this piece is pretty much the same.
Image used under Creative Commons from Mike Mozart
Table of Contents
- What is Cooking Oil, Exactly?
- Does Cooking Oil Go Bad?
- How to Tell if Cooking Oil Is Bad?
- How Long Does Cooking Oil Last?
- How to Store Cooking Oil
- Cooking Oil Shelf Life and Spoilage Summary
What is Cooking Oil, Exactly?
In theory, cooking oil is an umbrella term for every oil that you can use to cook with. The list is pretty extensive and includes both vegetable oils and animal fats such as butter, lard, or even bacon grease.
Fortunately, when buying a bottle labeled “cooking oil,” you don’t have to guess or even read the label to know what’s inside. In most cases, you’re buying refined soybean oil, canola oil, sunflower oil, or avocado oil.
These oils have a few things in common besides being refined. They:
- have a relatively high smoke point, making them good for stir-frying, deep frying, and other cooking techniques that involve high temperatures
- have a pretty neutral smell and taste, so they don’t affect the flavor of the food you’re cooking in them that much
- last quite some time, and don’t go rancid easily
Having that covered, let’s talk about the spoilage signs of cooking oil.
Does Cooking Oil Go Bad?
Cooking oil doesn’t last forever. The most common way it spoils is by going rancid, which happens if it’s stored for too long or in poor conditions.
You can tell your cooking oil is rancid if it’s bitter or sharp, or gives off an off-putting smell similar to old paint or nail polish remover. The aroma change isn’t always obvious, but the taste usually is, given that the oil is supposed to have a neutral taste.
Rancidification is an ongoing process, so in the beginning, you might notice a tiny change in flavor that will grow over time. Or you might not notice it at all if you use the oil regularly.
(But if that was the case, you’d probably use it up before it spoils, right?)
Noticing a dramatic change in flavor usually happens when the oil sits unused for a couple of months. It tasted okay when you last used it three months ago, but now it’s terrible.
Nevertheless, the best advice I can give you here is to use the oil for as long as its quality is okay and toss it once it starts to taste bitter or sharp.
(Don’t worry about eating a bit of rancid oil. It shouldn’t have any negative consequences in the short term, but doing so regularly and in larger amounts isn’t a good idea, as it might have detrimental effects on your long-term health.)
That said, going rancid isn’t the only sign of spoiled cooking oil. Let’s discuss others.
How to Tell if Cooking Oil Is Bad?
Discard cooking oil when:
- It smells off. If the oil is rancid, it might smell like some chemical solvent or nail polish remover. But if it gives off any other off-putting aroma, it’s likely bad too. Remember: cooking oil typically smells neutral, so if it doesn’t, something has changed.
- It’s bitter or sharp. Those two qualities are typical for rancid oil, so if they apply to your cooking oil, you know what you’re dealing with.
- There are nasties in the bottle. Check the bottle’s surface, bottom, and neck for any contaminants, “nasties,” or anything else that shouldn’t be there. Please note that cooking oil might become cloudy if refrigerated, and that’s okay.
- Its quality is bad after several uses. If you reuse it, there are a couple of signs of overused oil: deep-fried food is greasy instead of crisp, there’s foam on the surface, the oil has darkened, or it’s starting to smoke before it reaches the target temperature. For more on reusing oil, check out my article on peanut oil.
Those are the typical spoilage signs. But if you notice anything else that doesn’t seem right, trust your gut and grab a fresh bottle. Better safe than sorry.
Next up, let’s cover the shelf life of cooking oil.
How Long Does Cooking Oil Last?
Cooking oils last about 2 years unopened and around 6 months after opening. That’s assuming you store them sealed tightly and sitting in a cool and dark place, away from sunlight and heat sources.
Despite different oils being sold as cooking oil, their shelf lives are pretty much the same. Except for the shelf life of olive oil, which is a bit shorter, most other oils have a fairly similar storage time.
Those two years and six months are what you’re likely to find printed on the bottle. But if you take good care of the oil, you’ll likely get a few extra months without much quality loss.
Plus, refined oils (pretty much all oils sold as cooking oils are refined) tend to last longer than unrefined (or virgin) ones, so those two periods are quite conservative.
Last, you might be wondering why the sudden drop to only half a year of storage time after opening. That’s because once you open the bottle for the first time, its contents get access to fresh air, speeding up the rancidification process.
(More on that in the storage section.)
Now, let’s talk about “expired” cooking oil.
Expired Cooking Oil
Every bottle of cooking oil comes with a date printed on the label. That date is a best-by date, and it’s a rough estimate of how long the product should retain top quality. It’s not an expiration date that’s supposed to indicate when you toss the oil.
Sure, some sellers ask you to toss the oil when it goes beyond the printed date, but there’s little reason to do so based solely on that date.
In other words, using “expired” cooking oil is okay, as long as its quality is decent and it doesn’t show any spoilage signs. Nothing bad will happen just because the oil is past its date.
That’s not to say that the printed date is completely useless. Far from it.
Once your oil goes beyond its date, it’s time to pay more attention to its quality. That means tasting it before using it and perhaps asking your spouse or significant other for their opinion if you’re not sure if the oil is good or not.
And if the oil is a couple of months beyond its date and you’re not entirely sure it’s okay, assume it’s not.
Next time you open a bottle of cooking oil, give it a taste, so you know how it’s supposed to taste.
Storage is the last piece of the puzzle, and that’s what we’ll discuss next. Fortunately, it’s not that difficult to store your cooking oil so that it lasts a couple of extra months beyond its date.
How to Store Cooking Oil
Your cooking oil should sit in a cool and dark place, away from sunlight and heat sources. And once you first open it, seal it tightly every time you put it back in storage.
To retain its quality for a bit longer, you can refrigerate your cooking oil, but that’s definitely not a must.
If you store your cooking oil in the fridge, it might become a bit cloudy. You can reverse that effect by warming it up to room temperature.
If you’re using cooking oil for a salad dressing, make sure it’s room temperature before mixing it with other ingredients.
That said, refined oils don’t go rancid as quickly as unrefined ones, so refrigeration is rarely needed, even if it’s quite hot outside and you’re not blasting AC all day long.
Finally, remember that oils don’t like air, heat, and light.
That means storing it near the stove is not an option. And if the bottle must sit on the counter, make sure it’s not in direct sunlight, and use a dark-tinted bottle or canister to store it. That will help filter out some of the light, helping the fat retain quality longer.
Cooking Oil Shelf Life and Spoilage Summary
Thanks for reading this primer on cooking oil. Here are the key takeaways:
- Cooking oil goes rancid if stored for too long or in poor conditions. You can tell that yours is rancid if it tastes bitter or sharp, or smells like old paint or nail polish remover.
- Cooking oil lasts at least 2 years unopened and 6 months after opening. That’s what you find on oil bottles, but since these oils are refined, they usually last a few months longer. You can use them as long as they don’t show any signs of spoilage, even if they’re a couple of months past the date printed on the label.
- Store cooking oil sealed tightly and in a cool and dark place, away from any heat sources. If you want to prolong its shelf life even further, consider refrigeration.