Keep Your Oil in the Shade
Should you keep oil in the pantry or the refrigerator? For the most part, you should store oil in the refrigerator, or at least in a cool, dry place. There is, of course, an exception to every rule -- some varieties of extra virgin olive oil, for example, shouldn't go in the refrigerator. Condensation can develop within the bottle, which will affect the flavor. (Always be sure to read the product label to find the manufacturer's recommendation for that specific type of oil.) Both light and heat have a detrimental effect on oil. Darker containers can help, but that will only add a brief span to the shelf life if it's left in a well-lit area. Oxygen will also speed up the process of decay, and for that reason many oil manufacturers will fill the negative space in the bottle with an inert gas such as nitrogen. Most oils will thicken when refrigerated, but they'll quickly return to a liquid state when left standing at room temperature.
Then there's the question of containers. Traditionally, dark glass bottles are best for most types of oil; the dark color protects the oil from light, and glass doesn't interact with the oil itself. However, stainless steel, ceramic and porcelain vessels are all good alternatives. And unless you work in a restaurant that quickly goes through a lot of cooking oil, avoid plastic storage containers: The oil can absorb chemicals from plastic, including polyvinyl chlorides (PVCs).