It is good practice to buy oil in small sizes, or to split larger bottles with friends. If you purchase oil in bulk you should always pour it into smaller containers, preferably in a can or a dark-colored bottle.
You must remember…. “Olives are fruit; olive oil is a fruit juice.” So just like with any other fruit, air, heat, and light will cause olive oil to turn rancid (rancid is the flavor which the oil develops when it has started to oxidize). Since prolonged contact with air is the root cause of oxidation, rancidity is a common defect. Olive oil should therefore be stored in a cool and dark place in an airtight container). If your oil has a buttery taste, it is probably rancid.
When storing oil, keep in mind that the ideal temperature is 57°F or 14°C, although a normal room temperature of 70ºF works well if the olive oil is stored in a dark area where the temperature remains fairly constant. If you decide to use a kitchen cabinet that is away from the stove and away from direct sunlight, that will work as well. Better yet, if you have a wine cellar, store your olive oils there and keep a small amount in your kitchen. A big no-no is to leave the olive oil in a container without a tight cap. This will certainly set your oil up for a fast death. Make sure that the bottles are tightly sealed.
As we know it, refrigeration does not harm most grades of olive oil, but it is not recommended for expensive extra virgin varieties because condensation may develop inside the bottle, which may in turn affect the flavor. When chilled, or in cold weather, the oil may turn cloudy and even solidify but such oil will clear again as it warms. This cloudiness should not be taken as an indication that the oil is past its prime.
Tinted glass, porcelain, or stainless steel is the best material for storage containers; oil should never be stored in plastic or in reactive metals. Stay away from plastic containers as the oil can absorb PVCs.