Don’t panic, here are the reasons for the increase and emulsification of engine oil!

Text/Qian Jiaqing

Recently, some netizens posted reports that their Lexus or Toyota models have increased or emulsified engine oil. In view of the increasing attention on this incident on the Internet, in order to explore the truth, we also tried to give our own analysis.

The above picture material comes from the car quality network

According to AutoLab's investigation, the models with increased engine oil or emulsification are mainly concentrated in the Asia Dragon 2.5L Twin Engine and Camry 2.5HG ( Hybrid version), RVA4 Rongfang 2.5L dual engine and Lexus ES?300h. In addition, some gasoline models also have examples.

It is not difficult to find that the models experiencing this phenomenon are generally equipped with Toyota/Lexus hybrid systems, equipped with a 2.5L four-cylinder naturally aspirated engine code-named A25B. This power system is basically recognized as the best hybrid system on the market. It is known for its excellent energy consumption performance, reliability and smoothness. It is also the most widely used hybrid system in the Toyota Group.

After this phenomenon occurred, the outside world generally had two guesses about the cause.

One is related to a recall in the U.S. market some time ago, because there were defects in the manufacturing of the engine block, resulting in coolant being mixed into the engine oil; the other is related to the 2018 Honda "engine throttle" Similarly, due to weather and engine operation, gasoline and water vapor are mixed into the engine oil.

Guess 1: "Same origin" as the U.S. recall?

Soon after this incident, some netizens thought that Toyota had recalled the Avalon Hybrid, Camry, Camry Hybrid, RVA4, RVA4 Hybrid, Lexus ES?300h and other equipment in North America in early February. This engine model was removed on the grounds that the pores in the engine casting may cause cracks in the cylinder block, causing the vehicle's coolant to leak from the inside/outside.

This association seems unreasonable on the surface. If there are gaps in the engine, coolant may mix into the engine oil along the cracks, and eventually flow into the oil tank together, causing an increase in engine oil. Moreover, 60% of the coolant is water, and the engine oil will indeed emulsify after high-speed stirring.

But after careful consideration, there are many doubts about this matter

1. The US recall notice only mentioned the leakage of antifreeze and did not mention the phenomenon of oil increase and emulsification

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2. Domestic models with increased oil and emulsification do not seem to mention the reduction of coolant

3. The A25 series engines supplied to the US market are produced in the US and supplied to the Chinese market. The A25 series engines are mainly imported from the Japanese market, and there is currently no news about an increase in oil and emulsification in the Japanese market

Through the above three points, we can basically conclude that the increase in oil/emulsification incident in the Chinese market this time , is not directly related to the recall notice previously issued in the US market.

Guess 2: Another "Honda throttle"?

There are also many netizens who speculate that this time Toyota is involved in Honda’s 2018 “throttle door” incident. At that time, the Honda 1.5T "Earth Dream" engine involved was Honda's main power system. Oil increased and emulsified in a large area, and hot-selling models such as CRV were even discontinued for a time.

After investigation, it was found that the specific cause of the Honda incident was that when the vehicle was cold started, the engine computer ECU would control the injector to perform two "pre-injections", but because the specific amount of fuel injection was not Control it well, and at the same time, the atomization rate of gasoline is not enough under low temperature conditions, so a small part of the gasoline will remain in liquid form on the cylinder wall, and will be scraped into the oil tank by the piston before evaporating, resulting in an increase in engine oil.

As for the emulsification phenomenon, it was also due to the low ambient temperature and high moisture content in the air. After the air passes through the combustion chamber, the water vapor in it will condense on the cylinder wall and be brought into the oil tank by the piston together with the gasoline, resulting in emulsification.

In other words, Honda's "engine accelerator" was a design defect, which ultimately ended in interviews with the General Administration of Quality Supervision, Inspection and Quarantine, the suspension of sales of some models, and eventually forced recalls.

The above picture material comes from the car quality network

However, we cannot simply apply the reason for Honda's "throttle" to Lexus/Toyota. First of all, the two are different in engine technology design. After all, one is a turbocharged engine and the other is a naturally aspirated engine.

In addition, the hybrid system used by Lexus and Toyota was put on the market at the end of 2017 and has already passed the test of two winters. Finally, the conditions for using the car this time are not exactly the same. In addition to low temperatures in winter, the extremely special epidemic has also greatly shortened the driving time and mileage of most people. According to our guess, this is more likely to be the final cause of this incident.

You must know that the current domestic average temperature is still low, and the temperature in the northern region is still below zero. Toyota's hybrid system will use an electric motor to drive the vehicle at low speeds. At this time, for the purpose of energy saving, the engine will be shut down.

However, if the vehicle frequently travels at medium or low speeds, the temperature in the cylinder cannot be stable, resulting in insufficient combustion. Whether it is atomized gasoline or water vapor in the air, it may remain in the cylinder due to incomplete combustion.

If the engine is shut down for an extended period of time, these gases will condense and form liquid, which will be scraped by the piston into the oil tank. At this time, the oil in the oil tank will increase. When the water in the oil cap and other places mixes with the engine oil, emulsification may also occur.

With this possibility in mind, it is very simple and feasible to avoid similar situations. As long as you avoid short distances or frequent low-speed driving as much as possible and keep the engine in normal operating condition, you can effectively solve the problem of oil increase and emulsification.

From a technical point of view, if there is a small increase in engine oil or slight emulsification near the oil cap, it can be solved by driving longer distances, and it will not affect performance, safety, etc. Influence.

Of course, under the current special circumstances, it is still not recommended that car owners drive for a long time. They can continue to observe whether there is an increase or emulsification after the epidemic is over.

At the same time, Lexus also provides 6 years/150,000 kilometers of free warranty and maintenance for hybrid models. Currently, most dealers have resumed work. Car owners can make an appointment in advance through the dealer and conduct relevant inspections. I believe Lexus’ The after-sales service is still satisfactory.

This article comes from the author of Autohome Chejiahao and does not represent the views and positions of Autohome.