Oils with low smoke points are usually the best to use for salad dressings. These oils are typically unrefined, retaining more of their healthful benefits and flavor. It's important to know the flavor your oil will impart in the salad dressing, and make sure it's complimentary. Oils with the lowest smoke points are extra virgin olive oil, flaxseed, walnut, and pumpkin seed oils. You can also use some oils with higher smoke points with delicious results, including avocado, sesame, and grapeseed oils. I keep extra virgin olive oil on hand for dressing, because it works well with most spices, has a great heart healthy profile, and is almost neutral in flavor and color.