🔍 Key Concepts

• Function of lube (lubricating) oil in a diesel engine, especially during starting • How temperature affects viscosity (thickness) of lubricating oil • The difference between problems caused by fuel oil issues vs. lube oil issues

💭 Think About

• Think about what happens to the thickness (viscosity) of lube oil when it is very cold. How would this affect moving parts during cranking? • Which of these choices sounds more like a fuel system problem rather than a lube oil problem? Eliminate those first. • During engine start, what condition would make it harder for the engine to turn over and fire, if the oil is thick and sluggish?

✅ Before You Answer

• Identify which options describe symptoms of a fuel system issue and which describe a mechanical resistance / friction issue. • Ask yourself: Does cold, thick lube oil tend to make moving parts easier or harder to move? Which option matches that effect? • Verify which option describes a problem occurring right at starting/cranking, when oil is coldest and has not yet circulated fully.