🔍 Key Concepts

• Used lube oil analysis and what different contaminants usually mean • The typical source of sodium / nitrite compounds on a diesel or gasoline engine • Differences between problems caused by air filtration, fuel dilution, coolant leaks, and worn rings

💭 Think About

• For each choice, ask yourself: what specific chemical or physical sign would that problem leave in the lube oil? Would it produce sodium nitrite in high concentration? • Think about what is inside engine coolant versus what is in fuel and intake air. Which of those normally contains sodium-based additives? • Which condition would also tend to show up as a change in oil level, oil appearance (color/emulsion), or viscosity along with the chemical indicator?

✅ Before You Answer

• Match sodium / nitrite specifically with the system that commonly uses these compounds as corrosion inhibitors or antifreeze additives. • Eliminate options that would more likely show metal wear particles, soot, or fuel dilution instead of sodium nitrite. • Consider what other symptoms the engineer would probably also notice: rising sump level, milky oil, or loss of coolant in one of the systems.