Some of you may already know this, it might not be a good thing to mix different types or brands of antifreeze.
I've seen where types were mixed like when checking & filling the radiator & afterwards the mix turned to a slime & then when the engine was hot, it turned to solid.
Once it turns solid, that will be a costly repair, so be sure you know what type of antifreeze is in the radiator first before adding any.
If you dont know, best thing would be to drain the system completely & replace, making note of the type you filled the system with.
Neil