🔍 Key Concepts

• Normal combustion characteristics of a properly tuned diesel engine • What different smoke colors (blue, black, white/gray) usually indicate about engine condition • Effect of engine load on visible exhaust appearance

💭 Think About

• Think about what a well-maintained diesel engine looks like at sea when it is warmed up and running at its normal operating load. • Which exhaust color would suggest incomplete combustion or burning oil, and which would suggest clean, efficient burning of fuel? • If you can see a distinct color in the exhaust from a distance, what might that say about how ‘normal’ the engine operation is?

✅ Before You Answer

• Identify which options suggest oil burning or unburned fuel rather than normal operation. • Consider how much exhaust should be visible from a properly adjusted diesel under steady load. • Eliminate any choice that clearly indicates abnormal combustion or engine trouble.