What Causes Engine Oil Emulsification?
4 Answers
Engine oil emulsification is caused by water mixing into the oil. The specific reasons and solutions are as follows: The causes of water entering the engine oil are: 1. Cracked water cavity in the heat exchanger leading to water leakage into the oil. 2. Poor sealing of the cylinder head or cracked water cavity, loose sealing of the cylinder liner water jacket, cylinder liner cavitation, allowing water from the combustion chamber to enter the oil. Emulsified oil will have reduced oil film strength, failing to meet the lubrication requirements of the engine, and thus needs to be replaced. The solutions for engine oil emulsification are: 1. Clean the engine and replace the oil. 2. Clean the air filter chamber, exhaust pipe, carburetor, and exhaust joint. 3. Fill the engine with kerosene, repeatedly start and shut off the engine, ensuring the burning time does not exceed 30 seconds, then replace with new kerosene.
The other day I came across a classic case of oil emulsification during car repair. In most cases, it's caused by water mixing into the engine oil - when engine gaskets age and develop micro-gaps, coolant slowly seeps into the oil pan, turning the oil into milky white foam immediately. This happens more frequently in winter, especially for people who frequently take short trips where the engine doesn't fully warm up before shutdown, causing moisture condensation in the crankcase to mix with oil. If water vapor produced by gasoline combustion enters the oil, it can also cause this, which usually indicates problems with the crankcase ventilation system. The worst scenario is when there are internal engine cracks allowing coolant to leak directly - these repairs can get expensive. Remember to check your dipstick monthly, and if you find mayonnaise-like oil, get it fixed immediately.
A veteran driver with 20 years of experience in the north tells you that 90% of oil emulsification is related to temperature. Frequent short trips in sub-zero temperatures are the most dangerous—driving only 3-5 kilometers each time, stopping just as the engine warms up, causes repeated condensation of water vapor, slowly filling the oil pan with a mixture of water and oil. Cars with design flaws are especially prone to this issue, such as those with poorly positioned oil-gas separators where cold air condenses directly into the engine oil. Last heavy snowfall, I specifically checked my son's car and found the separator full of frost. Now in winter, I've developed a habit of taking long drives to warm up the engine thoroughly, hitting the highway weekly to let the engine 'sweat out' and evaporate the moisture.
Discussing oil emulsification from a chemical perspective: Essentially, it's the mixing of incompatible liquids into the lubricating oil. When oil and water mix, surface-active substances form an emulsification film, much like a whisk blending cream. During daily driving, blow-by gases from the combustion chamber carry acidic water vapor that penetrates the piston rings, and low-quality oils with poor anti-emulsification properties fall victim. Even worse is ethanol gasoline, which has strong hygroscopicity and generates formic acid that corrodes metals. The most severe case I've seen involved mixing different brands of motor oil, where additive reactions accelerated emulsification. It's recommended to develop a habit of warming up the engine, choose polyalphaolefin-based full synthetic oils to enhance anti-emulsification properties, and regularly check the air filter.
