🔍 Key Concepts

• Thermal expansion of engine oil (cold vs hot) and how it affects level readings • Difference between checking oil level with engine stopped versus idling/running • Why manufacturer provides two different calibrated scales on some dipsticks

💭 Think About

• Think about what happens to the oil level in the crankcase when the engine is stopped and cold compared to when it has been running and is fully warmed up. • Consider whether the oil level in the sump appears higher or lower when a large quantity of oil is circulating through the engine and trapped in galleries and filters. • Ask yourself why it would be unsafe or misleading to use the same dipstick marks regardless of temperature and whether the engine is running or stopped.

✅ Before You Answer

• Identify which condition would give the lowest apparent oil level in the sump: stopped/cold, stopped/hot, idling/cold, or idling/hot. • Determine under which condition the manufacturer most likely wants the standard reference level set (think of normal operating state of the engine). • Eliminate any options that ignore the effects of oil circulation and thermal expansion on the reading.