🔍 Key Concepts

• Detergent-type lubricating oil purpose in diesel engines • How carbon and soot are handled in modern engine oils • Difference between oil that is contaminated or broken down vs oil that is simply dark or black

💭 Think About

• Ask yourself: what is the main job of detergent additives in lubricating oil inside a diesel engine? • Does black color always mean the oil is unfit for service, or can it sometimes mean the oil is doing its job? • Which option best describes a condition the oil is in, rather than a maintenance action you must take?

✅ Before You Answer

• Check which choice explains why the oil is black, instead of telling you what maintenance to perform. • Verify your understanding that diesel combustion produces soot/carbon and consider how detergent oil is designed to deal with that. • Be sure the option you pick matches the normal, expected behavior of detergent oil in a working diesel, not an emergency or abnormal condition.