“Unlike wine, oil deteriorates,” says chef and cookbook author Paula Wolfert, “The better oils give you the year it was produced.” The shelf life for a really good extra-virgin olive oil is about two years. The label tells you a minimum of one important distinction: Extra Virgin. The International Olive Oil Commission (IOOC) has established that name to indicate that the oil was cold pressed, and that no chemicals were introduced to aid in extraction. It also indicates an acidity of less than 1 percent, which cannot be detected by taste. Oil must be analyzed in a laboratory to ascertain acidity level. “That's really important, because it means that the oil has all of its vitamins in it.”