The fluid currently in the system appears a medium brown shade. The bottle of chf-11s seems to contain a blue colored fluid. I don't wish to lay waste to my entire system by mixing fluids. (btw, never use the Lucas PS Stop Leak with chf-11s. I decided to contact them before adding it. Not compatible!). What is my best course of action? If I thoroughly purge the system of the current fluid will I be ok to refill with Pentosin chf-11s? I need to take care of this asap so any assistance is certainly appreciated.