🔍 Key Concepts
• Sludge formation in lube oil systems and what it looks like
• How water, fuel, and combustion by‑products can contaminate lube oil
• Where contaminants enter a diesel engine lube oil system (combustion chambers, crankcase, cooling leaks)
💭 Think About
• Think about every realistic way foreign material can get into the lube oil: from combustion, from leaks, and from incomplete fuel burning near the piston rings.
• Consider whether sludge usually comes from just one source or from a combination of several different contamination processes.
• Ask yourself which options describe mechanisms that would actually mix with, or chemically affect, the lube oil to create thick, sticky deposits rather than cleanly burning away.
✅ Before You Answer
• Check which choices clearly involve oil mixing with other substances (water, fuel, combustion products).
• Verify in your diesel engine knowledge whether water in the lube oil tends to create sludge or some other type of problem.
• Before choosing, ask: does sludge in practice come from only one of these causes, or can it result from multiple contributing factors?