26 Refining Used Lubricating Oils
1.6.7 Blended Oils
Blended oils (compounded oils) are lubricating oils in which the properties are improved
by the addition of additives. Additives enhance certain desirable properties of the base
lubricating oil or give it new desired properties. Additives that improve oiliness include
fatty acids, castor oil, and coconut oil. Antioxidant additives include phenolic com-
pounds and amino compounds. Antifoaming agents that are added to lubricating oils
include glycerol and glycols, emulsifying additives include sulfuric acid and sodium
salts, and viscosity index–improving additives include compounds with high molecu-
lar weights, such as hexanol (C
6
H
13
OH; n-hexanol, boiling point 158°C, 315°F).
However, moder