According to Vietnam’s General Standard on Food Labeling, the 18-month shelf life printed on cooking oil packaging only refers to the period during which the product may be circulated on the market under specified storage conditions.

So, how long can cooking oil actually be used after opening?

Currently, most supermarkets sell refined cooking oil in sealed packaging with a shelf life of about 18 months. If the seal remains intact and the oil is not exposed to air, its usability may last longer. However, cooking oil is meant for daily use, which means once the bottle is opened, its quality will be affected by multiple factors.

If a large container of oil is opened and poured into a household dispenser, then tightly sealed and stored in a cool, well-ventilated place, it can generally be used for about 1.5 years. In normal household conditions, however, a 5-liter container of cooking oil is usually consumed within 3–6 months, so expiration is rarely a concern.

How dangerous is expired cooking oil?

Changes in oil quality

When the oil container is not tightly sealed, exposure to air and moisture alters the oil’s flavor. The oil may develop an unpleasant odor, making food taste bad and requiring deodorization before use. Discarding spoiled oil also leads to waste—especially when large containers cost around 100 yuan each, which is a significant household expense. Using expired oil to save money can pose serious health risks.

Loss of nutritional value

Cooking oil is rich in nutrients and beneficial to health when consumed within its shelf life. However, once the oil expires, these nutrients begin to break down, causing the oil to lose both flavor and nutritional benefits. When exposed to air, this process happens rapidly—within about one week, most nutrients in the oil may be lost. Continued consumption of nutrient-depleted oil can lead to fatigue, obesity, and an increased risk of cardiovascular disease.

Degradation and risk of poisoning

Expired cooking oil deteriorates quickly and may allow bacteria to multiply. If used for cooking, it can seriously harm family members’ health. In severe cases, spoiled oil may cause acute poisoning, with symptoms such as nausea, vomiting, diarrhea, abdominal pain, and even the risk of chronic poisoning.

Accelerated aging

Long-term consumption of expired cooking oil not only affects the digestive system but also leads to the accumulation of harmful substances in the body. These toxins disrupt metabolism, accelerate skin aging, and may cause damage to skin tissues.