Great in sealed systems but once in the open air it will evaporate...dont believe the hype that half a coke can full in 400 litres will do as it this is no where near enough.
It does not affect the tds but you'll need 10's of litres of it per tank...
If you are getting night temps of down to minus 3 and day temps of +...then you'll not need anything..its when you have reoccuring sub 0 night temps followed by sub day temps that will cause you real problems....
Have a look at the back posts about this...there is loads of info.
Dave.