Corn oil is widely used in dressings. It has a light golden color and is nearly tasteless, except for a mild cornmeal-type flavor.
Cottonseed oil, soybean oil, canola oil, and safflower oil are bland, nearly tasteless oils. Vegetable oil or salad oil is a blend of oils and is popular because of its neutral flavor and relatively low cost.
Peanut oil has a mild but distinctive flavor and may be used in appropriate dressings. It is somewhat more expensive.
Olive oil has a distinctive, fruity flavor and aroma and a greenish color. The best olive oils are called virgin or extra-virgin, which means they are made from the first pressing of the olives. Because of its flavor, olive oil is not an all-purpose oil but may be used in specialty salads such as Caesar salad.
Walnut oil has a distinctive flavor and a high price. It is occasionally used in fine restaurants featuring specialty salads. Other nut and seed oils, such as hazelnut oil and grapeseed oil, are sometimes used.