Most salad dressings are based on oil and vinegar, or oil and the juice from a citrus fruit. They depend for their perfection on the quality of the oil and the acidity. A dressing made from blended vegetable oil and malt vinegar would be unspeakably disgusting and render any salad inedible. It is best to use olive oil, preferably the first pressing, which is labelled as extra virgin; this has the maximum amount of flavour from the olives. Other good oils that can be added to olive oil, or used alone, are walnut, hazelnut and toasted sesame, which will perfume and flavour a salad magnificently.