ASE G1 Auto Maintenance and Light RepairEngine SystemsEasy
During an oil change, a technician notices that the engine oil is milky and discolored, resembling a 'milkshake' consistency. The vehicle's coolant level is also noticeably low. What is the most likely cause of these observations?
- AAn internal coolant leak into the engine oil
- BOver-extended oil change intervals
- CExcessive moisture from short-trip driving
- DContamination from fuel injectors
Show answer & explanationAnswer & explanation
Correct answer: A. An internal coolant leak into the engine oil
Milky or milkshake-like engine oil, especially when accompanied by a low coolant level, is a classic symptom of coolant mixing with the engine oil, typically due to a blown head gasket or a cracked engine component.
Why the other options are wrong
- B. Over-extended oil change intervals would lead to very dark, sludgy oil, not milky oil.
- C. Excessive moisture from short trips can cause some condensation, but usually not to the extent of a 'milkshake' consistency with a noticeable coolant loss.
- D. Fuel contamination would thin the oil and cause a gasoline odor, not a milky appearance.
Coolant-in-Oil Symptoms
The presence of coolant in engine oil typically results in a milky, frothy, or 'milkshake' appearance of the oil, often accompanied by engine overheating or coolant loss.
- Milky oil indicates coolant contamination.
- Often caused by head gasket failure.
- Coolant level usually drops.
Memory trick: Milky oil is coolant's foil.