Walnut Oil is an oil made from walnuts. It has a very strong flavour. It is primarily valued in cooking for the depth of flavour that it can add; you usually use it in small quantities to enhance the flavours of salad dressings, etc.
To make Walnut Oil, the walnuts are first toasted to develop the flavour and loosen the oil. The walnuts are then cold pressed to extract the oil from them.Five pounds (2 kg) of walnuts are needed to make 1 litre of the oil.
The oil can be sold unrefined, or semi-refined.Unrefined Walnut Oil has a smoke point of 320 F (160 C); semi-refined Walnut Oil has a smoke point of 400 F (205 C.) Almost all Walnut Oil is unrefined, so you can see that its smoke point is pretty low to be frying or sautéing with this oil. But because it's quite expensive, and heat destroys the flavour, you wouldn't actually want to use it for frying, anyway.