🔍 Key Concepts

• combustion quality in diesel engines (incomplete vs complete combustion) • difference between white, blue, and black exhaust smoke and what each usually indicates • how engine temperature and load affect fuel ignition and vapor in the exhaust

💭 Think About

• Think about what white smoke actually is: is it unburned fuel, water vapor, or burning lube oil? Which condition from the choices would most likely produce that? • Compare the symptoms: if an engine is overloaded, what color is the smoke usually, and why? What about when lube oil is burning? • Ask yourself: in which situation would fuel be injected but not fully ignited, so that it passes into the exhaust as a visible mist?

✅ Before You Answer

• Match smoke color to common cause: white vs blue vs black • Consider how a cold cylinder affects fuel ignition in a diesel (compression ignition relies on air temperature) • Eliminate options that usually produce black smoke (soot from excess fuel) or blue smoke (burning lubricating oil) rather than white.