🔍 Key Concepts

• Diesel engine starting requirements (compression heat, air temperature, friction) • Effect of oil viscosity on moving parts at low temperatures • How cold temperatures change mechanical resistance in an engine

💭 Think About

• Think about what a diesel engine needs in order to start and how cold metal and cold oil might interfere with that. • Which option describes something that would make it physically harder for the crankshaft, pistons, and bearings to turn when the engine is cold? • Consider whether cold air or colder clearances would make starting easier or harder in a compression-ignition engine.

✅ Before You Answer

• Compare how oil viscosity changes in cold vs. warm conditions and what that does to internal friction. • Ask yourself if higher compression pressure in a diesel helps or hurts cold starting, and if any choice suggests that effect. • Eliminate any option that clearly would make starting easier, not harder, for a compression-ignition diesel engine.