🔍 Key Concepts

• Properties of good lubricating oil used in engines and machinery • Effects of acidity, oxidation, and emulsification on metal surfaces and bearings • Purpose of additives in modern lubricating oils

💭 Think About

• Think about what would happen to metal parts if the lubricating oil contained acid or oxidized rapidly. • Consider whether it is desirable for lubricating oil to mix easily with water, or to stay separated from it. • Ask yourself why manufacturers often put additives in lubricating oils—are they usually helpful or harmful to performance?

✅ Before You Answer

• Verify which property best protects metal surfaces and bearings over time. • Check which options describe things that are generally harmful in lubricating oil rather than helpful. • Confirm whether good lubricating oil should resist or promote emulsifying with water.