The mono-and polyunsaturated fat content of an edible oil is what determines the temperature at which it will solidity, what its burn point is in the frying pan, and how quickly contact with oxygen will turn it rancid. Olive oil consists of up to four-fifths monounsaturated fatty acids which makes it ideal for frying. The oil keeps best at about 15°C, and in the refrigerator it will turn cloudy with flaky lumps-but only until its temperature rises again. Whether or not this spoils the flavor is a matter of opinion.
Other oils with higher proportions of poly unsaturated fatty acids are more sensitive to heat and oxygen, and unrefined salad oils in particular keep longer under cool conditions. All types of edible oils are best stored in the dark or in dark-colored bottles.