🔍 Key Concepts

• How lube oil contamination occurs in diesel engines • The byproducts of fuel combustion (water, sulfur compounds, unburned fuel) • The difference between normal byproducts and actual contamination sources

💭 Think About

• Think about which combustion byproducts can physically enter the crankcase and mix with lube oil. • Consider how sulfur in the fuel affects the engine: does it contaminate the oil directly, or does it form something else that might? • Ask yourself whether unburned fuel oil can get past the piston rings and what effect that would have on lube oil.

✅ Before You Answer

• For each option, decide if it can realistically reach the lubricating oil system in normal or faulty operation. • Verify which byproducts can cause dilution, acidity, or sludge formation in the lube oil. • Double-check whether any of the listed factors are indirect causes (through chemical reactions) rather than direct physical mixing.