🔍 Key Concepts

• Color of exhaust smoke and what it indicates about fuel vs. air vs. lube oil in a diesel engine • How fuel atomization and combustion temperature affect visible exhaust • Difference between symptoms of incomplete combustion and oil burning

💭 Think About

• Think about what condition would allow unburned or partly burned fuel to pass into the exhaust without fully igniting. Which option describes that best? • Which of these choices would more likely produce blue or bluish smoke instead of white? Eliminate that. • If air is too much or too hot, what happens to the completeness of combustion and how visible is the exhaust?

✅ Before You Answer

• Match smoke color to cause: white vs. blue vs. black. • Consider whether lube oil consumption has a characteristic smoke color that is different from unburned fuel. • Ask: does late fuel injection tend to make combustion start earlier, on time, or later in the power stroke—and how would that affect whether fuel fully burns?