My MB mechanic told me that I did not have to fill up my radiator reservoir with coolant every time I needed a top up. He said plain water will suffice. Just curious what the forum thinks. Also, does the water level in the reservoir fluctuate while the car is being driven?
The level changes with temperature, so yes. You can fill with water if your coolant is not too diluted afterwords. I recommend distilled water, but it's a bit of overkill for the cooling system.
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