Maybe BMW coolant. They use a lot of magnesium in the block.https://en.wikipedia.org/wiki/BMW_N52
The N52 engine block is cast with magnesium and aluminum for the crankcase. Magnesium is used to save weight. However, magnesium is subject to a greater risk of corrosion from water, and magnesium may tend to creep under load at high temperatures. Thus, magnesium in its pure form or as a conventional alloy is not suited for permanently conveying high loads and forces of the kind typically encountered in central components of the engine. Therefore, BMW combined the N52 block to use magnesium alloy for the crankcase shell, with an aluminum “inner block” to complement the magnesium disadvantages.
Although, not sure if the coolant comes in contact with the magnesium or not.