The entire contents of the cooling system is ~ 4.5 gal and is a 50/50 mix Porsche coolant : distilled water.
Absolutely it's ok to add distilled water if you're just topping off the system. Say you're adding up to 1 gal (which would be a lot
)of distilled water - you'd still have a ~ 40:60 mix. Any more than that you should mix it 50/50.
Now, if you're in a pinch and need to be able to get somewhere you could fill the entire system w/ nothing but distilled water. Then, once you find/fix your leak, I'd adjust the mix back to 50/50 or relatively close to it.
