🔍 Key Concepts

• Oil oxidation in diesel engine lube oil systems • Effects of high temperature on lubricating oil chemistry • Formation of acids, sludge, and varnish in oxidized oil

💭 Think About

• Think about what chemical changes happen to oil when it is overheated over time, not just temporary thinning. • Which choice describes a long‑term damage mechanism inside the engine, rather than a short‑term operating symptom? • Which effect is most closely tied to the creation of unwanted compounds in the oil that can attack metal surfaces?

✅ Before You Answer

• Identify which option involves chemical by‑products versus simple physical changes (like thinning or foaming). • Ask: Does high temperature always cause the effect stated, or is that word "always" a red flag? • Consider which effect would most likely lead to corrosion of bearings and internal parts over time.