[Yuille36]

Let me first clarify. Intercooler fluid is simply your typical engine coolant. Your X5M has two different cooling systems. One for the engine coolant and the other for the turbo charging systems, to cool the intake charge to the engine.
Both systems with their own coolant reservoirs when you open your hood. As you already know, coolant does not last forever so it does need changing, so your system runs better.