Which of the additives listed is used to...

🔍 Key Concepts

• Behavior of lube oil when air is entrained and why foam is a problem in engines • Typical types of chemical additives used in lubricating oils and their primary functions • Difference between additives that promote mixing (like detergents/emulsifiers) and those that reduce or suppress unwanted behavior

💭 Think About

• Think about what you want to happen to foam in lube oil: do you want to create it, stabilize it, or get rid of it? • Look at each option and ask: does this additive generally increase mixing/stability of oil with other substances, or does it act to knock something down or prevent it? • Consider where the term is also used outside of lubrication, such as in fire-fighting agents or refrigerants, and what they do in that context.

✅ Before You Answer

• Match each term with its general industrial meaning (e.g., emulsifier, depressant, suppressant). • Eliminate any additive whose main function is to help oil mix with water or contaminants, since that would worsen foaming, not help it. • Confirm which term most clearly means to reduce or prevent an unwanted effect, like foam formation.

Which of the additives listed is used to reduce the foaming tendency of lube oil?

Emulsifiers

Suppressants

Depressants

Extreme pressure