09 1.4t Magotan accelerator has oil. What happened?

The reason is that the engine will produce exhaust gas when it is running. At the position of the air cleaner, there is a pipe connected to the upper cover of the engine to exhaust the exhaust gas. If the car is driven for a long time, it will always produce exhaust gas. Even if it can be discharged, it will definitely leave a little at a time. Over time, many a mickle makes a mickle.