Does Vegetable Oil Go Bad?

If you’re like me, at any given moment you have two or three half-open bottles of vegetable oil in the kitchen cupboard. You use some of them for frying and sautéing, others as a base for salad dressing. Inevitably, you notice that one of the oils is past the date on the label. Does vegetable oil go bad?

There are many vegetable oils available on the market, but they all share very similar characteristics. If you were to learn those basics, you would be prepared to deal with pretty much all kinds of veggie oils available. If you would like to learn about storage, shelf life, and going bad of vegetable oils, read on.

Vegetable Oil
(credit: cottonseedoil )

How To Store Vegetable Oil

A cool and dark place is where you should store vegetable oils. Make sure it’s away from sources of heat, so the temperature doesn’t fluctuate. Frequent temperature changes negatively affect the oil. Also, remember to keep the oil away from sunlight and artificial lights. Light speeds up the oxidation process of oils, and we don’t want that to happen. The pantry is probably the perfect place to keep an unopened bottle of vegetable oil.

Once you open the bottle, the first thing you should remember is that it needs to be sealed tightly. No matter if it’s canola, grapeseed oil, EVOO, or any other oil, if you’re not using it at the moment, the lead needs to be sealed. Unsealed bottle means the oil has free access to oxygen and that accelerates oxidation too. Since the pantry probably isn’t the most practical place to keep oil that you use fairly often, you can transfer the bottle to a kitchen cupboard, so it’s easy to grab when needed.

Storing opened bottle of vegetable oil in the fridge is also an option, especially if you live in a hot and humid area. Please note that some oils become cloudy at chilly temperatures. That process is harmless and doesn’t affect the quality of the oil. Once the oil reaches room temperature, its usual consistency will be restored too. If the oil stored in the fridge starts to become difficult to pour, you may need to put it on the counter about an hour before using, so it’s smooth when you need it. Please note that if you use a bottle of such oil often, there’s no point in keeping it in the fridge. That’s because the frequent cooling and warming will degrade the quality of the fat.

How Long Does Vegetable Oil Last

Vegetable (and cooking) oils usually come with a best-by date on the label. That date informs you how long the oil should retain freshness. Of course, that date is an estimate, and the oil, if stored properly, will keep fresh for longer. It’s impossible to tell how long beyond the date on the label the oil will be at peak quality. It depends on storage conditions, the type of oil, and the quality of the fat. Oils from reputable brands usually last longer, but they also cost more. In short, you can expect that vegetable oil should last for a few months up to half a year past the best-by date. That’s, of course, a rough estimate.

Once you open the bottle, the liquid gets access to new air, and the oxidation process speeds up a bit. That pretty much means that a half-open bottle degrades in quality faster than an unopened one. Nevertheless, the process is gradual, and if you oil isn’t old already, it should last in good condition at least 6 to 12 months. Again, these periods are only estimates.

Vegetable oil (unopened) Best by + 3 – 6 months
Vegetable oil (opened) 6 – 12 months

Please note that the periods above are estimates and for best quality only. Vegetable and cooking oils usually stay safe to use for much longer, but the quality isn’t necessarily that great.

How To Tell If Vegetable Oil Is Bad

Let’s start with spoilage of vegetable oils. Since oils are pretty much fat and nothing else, they usually don’t go bad in the traditional sense, meaning they don’t suddenly become unsafe to eat. Nevertheless, if you notice anything that makes you question if the oil is still okay to eat, throw it out. Some of the signs might be a change of color, mold near the seal, or an off smell.

What’s much more probably is that the oil goes rancid. The presence of oxygen, light, or temperature fluctuations speed up the process of rancidification. So if you take good care of your vegetable oils, they will last a long time, but if you accidentally put a bottle in a cupboard above the stove, it will go rancid in a few months. Spotting a rancid oil is sometimes difficult. Especially if don’t really know how a fresh one should taste. Most descriptions point to slight darkening of the liquid, altered smell, and a stale taste. In short, the changes are often quite subtle and almost impossible to spot for some of us.

What’s most important about rancid oil is that it is safe to eat. The nutritional profile of the fat might change a bit, but it won’t make you sick. The worst case scenario is that the salad dressing you used the oil in won’t taste as good as it used to. So whenever you spot a bottle of rancid oil, it’s up to you if you throw it out or continue using it. Of course, if the oil tastes really bad, just throw it out. It will ruin pretty much any dish you use it in, so there’s no point in keeping it around.