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.

https://www.rt-mart.com.tw/tainan/index.php?action=product_detail&web_lang=en&prod_no=P0159300891735

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.