🔍 Key Concepts

• Effect of low temperature on lube oil viscosity in diesel engines • Relationship between viscosity and ability of parts to move/slide • What factors actually change mechanical friction during engine start

💭 Think About

• Think about what happens to lubricating oil when temperatures drop below 70°F: does it get thinner or thicker, and how does that affect friction? • Which of the options describes a condition that changes with temperature in a way that would directly affect turning resistance? • Consider which choices are realistic: can an operator easily change compression ratio or completely eliminate friction just by heating intake air?

✅ Before You Answer

• Identify which option involves a property that varies strongly with temperature. • Check which factor is directly tied to how easily moving parts slide over each other. • Eliminate any answers that suggest you can totally eliminate friction, or that are not practically adjustable during normal operation.