🔍 Key Concepts

• Normal combustion characteristics of a healthy diesel engine • What different exhaust colors (blue, black, white, gray, clear) usually indicate about engine condition • How fuel burn efficiency and oil burning show up in exhaust appearance

💭 Think About

• Think about what you typically see from a well‑maintained modern diesel running at normal operating temperature and load • Which color would more likely indicate burning lubricating oil or incomplete fuel combustion rather than normal operation? • If an engine is tuned correctly and burning clean fuel efficiently, how noticeable should its exhaust be?

✅ Before You Answer

• Identify which choices suggest oil burning (often blue‑tinted smoke) versus normal operation • Consider which options imply visible particulates or unburned fuel (darker haze) rather than clean combustion • Ask whether a properly operating diesel should have clearly visible exhaust under steady load and warm conditions