What does the milky substance on the oil cap indicate?
2 Answers
Finding a milky substance on the oil cap indicates that the engine oil has undergone emulsification, meaning the oil has deteriorated and its performance has declined. The reduced lubrication effect accelerates wear on moving parts, rendering the oil unfit for continued use. Here are methods to identify oil emulsification: 1. Visually inspect the oil's state and color. When pulling out the dipstick, a small amount of oil will come with it; check if it appears as a milky, bubbly liquid. 2. Open the oil cap and look inside the oil filler port or directly at the oil cap for any milky, bubbly substance. The presence of significant milky bubbles indicates oil emulsification, necessitating immediate fault diagnosis and oil replacement. If the oil appears normal light yellow or black, it is in good condition. 3. Another sign of water contamination in the oil is an increase in oil volume. Under normal circumstances, the oil level should remain constant or decrease. If the oil level rises above the maximum mark, it indicates a problem.
I've been driving for over 20 years and often encounter this issue. A milky white substance appears on the oil cap, resembling the color of milk, which is usually the result of oil mixing with water. The common cause is frequent short-distance driving, especially in cold weather when the engine doesn't fully warm up, allowing moisture to condense in the oil. It could also be due to a damaged engine gasket or cracks in the cylinder, causing coolant to leak into the oil system. Once, I ignored it when I found it, and the oil deteriorated, leading to engine overheating, which cost me thousands to repair. It's best to immediately check the coolant level; if it's low or has foam, that might be the issue. Regularly inspecting the oil condition and driving on highways to fully warm up the engine can reduce condensation. If you notice this milky substance, don't delay—take it to a professional repair shop to avoid bigger losses.
