Here's why:
* Separate Systems: Engine oil and transmission fluid operate in completely separate systems. The engine has its own oil pan, pump, and filter, while the transmission has its own distinct fluid reservoir, pump, and filter.
* Physical Barriers: A strong, sealed barrier separates the engine and transmission. This barrier is usually a metal plate or casting that prevents any fluid from crossing over.
* Different Types of Oil: Engine oil and transmission fluid are specifically formulated for their respective jobs. They have different viscosity, additives, and properties. Mixing them would be detrimental to both systems.
However, there are some scenarios where you might see fluid mixing, but it's not a direct drainage:
* Seal Failure: A severe leak in a seal between the engine and transmission could allow a small amount of fluid to leak across. This is rare but possible.
* Overfilling: Overfilling the transmission can sometimes lead to a small amount of fluid spilling over into the engine oil pan if there's no proper drain back system.
It's crucial to remember: Any fluid mixing between the engine and transmission is a serious problem that requires immediate attention from a qualified mechanic.
