🔍 Key Concepts

• viscosity and how it changes with temperature • the definition of viscosity index in lubricating oils • what neutralization number and demulsibility actually measure

💭 Think About

• Ask yourself: does a high viscosity index mean the oil’s viscosity changes a lot with temperature, or only a little? • Consider which property (viscosity index, neutralization number, demulsibility) is directly linked to thickness change with temperature, not to acidity or water separation. • Think about an oil that stays almost the same thickness from cold start to hot running conditions – would that have a high or low viscosity index?

✅ Before You Answer

• Make sure you know that viscosity index describes how strongly viscosity changes with temperature. • Confirm that neutralization number is related to acidity/alkalinity, not thickness change. • Verify that demulsibility deals with how easily oil separates from water, not with temperature-thickness behavior.