prestone coolant

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interesting points here:

i called the dealership, the parts department guy said porsche coolant is not compatible with any aftermarket coolant, prestone included.

I then called the service department of the same dealership and the person said it was fine to top up with same/similair color coolant as long as the coolant added was not green in color. the added coolant had to be the yellowish/orange color.

I then followed up and tried to book a coolant flush appointment, and they refusued it, as the coolant is lifetime and they dont do or advise any flushes being done.

mentioned to them my situation, as i only topped up from min to max, they let me know the min/max only measures the coolant overflow tank is approx 2L, while whole coolant tank is around 16L. so it should not harm anything. are these figures accurate? Havent got a chance to check my manual yet.

I am rather confused now. any more insight into this?