Additives can make a major difference in a gasoline's performance. For nearly 40 years, every gallon of motor gasoline sold at the pump has contained up to a half dozen different additives - ranging from a few drops for minimally treated unleaded gasoline to about six milliliters for fully leaded gasoline. The additives used in gasoline, their chemical types, and functions are summarized. Some additives are injected at the refinery. These additives are designed to help the product meet ASTM gasoline specifications as well as the individual requirements of multiple customers.