Sonax Radiator Rust Preventer

Be replacing my coolant soon, since I had to do an emergency top-up with flaky water from a hose, and I will lose some more if I get the temperature sensor out for testing. Seems stuck.

I used cheapo green stuff with Chinese writing on it last time, from RT-Mart, and I’m not very convinced, though I think I’ve got another couple of litres of it somewhere…

They had Sonax Radiator Rust Preventer at about 3 times the price, which is supposed to be compatible with antifreeze, It makes sense to use corrosion prevention (if it works) rather than antifreeze in Taiwan.

Anything known about this stuff?

Packaging makes a thing about it being German, which I always find suspicious here, but Googling mostly gets SE Asian and Egyptian sites.

They also had conventional Shellzone antifreeze at about the same price, which might be a safer bet.