During preflight, the engine oil level should be between the bottom of the sight glass and the __ line if checking __ than 15 minutes after shutdown.

During preflight, the engine oil level should be between the bottom of the sight glass and the __ line if checking __ than 15 minutes after shutdown.

• A. Top of sight glass and Min
• B. Bottom of sight glass and Max
• C. Top of sight glass and Max
• D. Bottom of sight glass and Min

Answer: (D)

When you perform a preflight oil check, you allow the oil time to settle after shutdown so the reading reflects the actual sump level rather than a transient condition. With more than 15 minutes elapsed, the oil has drained back and settled toward the lower end of the sight glass range. The correct reading is therefore the oil level shown between the bottom of the sight glass and the Min line. The bottom marks the lower limit you can see, and the Min line represents the minimum acceptable level. Keeping the reading in this lower range confirms there is enough oil to protect the engine without relying on a higher, unsettled indication that could occur right after shutdown. Reading above the Min line could suggest an overfill condition or a reading influenced by oil still shifting after shutdown, which is not the intended preflight check window.

When you perform a preflight oil check, you allow the oil time to settle after shutdown so the reading reflects the actual sump level rather than a transient condition. With more than 15 minutes elapsed, the oil has drained back and settled toward the lower end of the sight glass range. The correct reading is therefore the oil level shown between the bottom of the sight glass and the Min line. The bottom marks the lower limit you can see, and the Min line represents the minimum acceptable level. Keeping the reading in this lower range confirms there is enough oil to protect the engine without relying on a higher, unsettled indication that could occur right after shutdown. Reading above the Min line could suggest an overfill condition or a reading influenced by oil still shifting after shutdown, which is not the intended preflight check window.