🔍 Key Concepts

• viscosity and how it changes with temperature • the meaning of viscosity index in lubrication engineering • differences between pour point and general viscosity measures

💭 Think About

• Which option specifically describes how much viscosity changes as temperature goes up or down, not just the thickness of the oil at one temperature? • Which term is commonly used on lubricant data sheets to compare how stable an oil’s viscosity is over a range of temperatures? • Which option is clearly about flow at low temperature only, and which is about general temperature–viscosity stability?

✅ Before You Answer

• Verify which term is defined as a measure of the change of viscosity with temperature • Eliminate any choice that only refers to low-temperature flow characteristics (cold flow / minimum pumping temperature) • Check which of these appears on typical engine oil specifications along with SAE grade and pour point