I am using pre-diluted (50:50) coolant in my car. I have observed that with passage of time and use (around 4 month), coolant quantity in reservoir bottle decreases to middle of MIN and MAX.
I have a question that should I top up the reservoir bottle to MAX level with same coolant or should I top up reservoir bobble with distilled water only?
I heard from someone that for top up purpose only use distilled water instead of coolant because only water evaporates with passage of time not the coolant chemical. so if you keep adding coolant, it will increase the coolant to water ratio and may damage radiator and engine system.