Operating temperature is normal. (Electric aftermarket temp gauge) It has a very, very minor leak in the radiator and has for a year at least. It’s gotten no worse. I’ve never used any additives myself but can’t speak for previous owners. I add 50/50 conventional green to the bottle as needed. Radiator is always full when I check it cold. Is it just needing a good flush? If I stick in my finger and wipe the inside of the radiation, I get a thin layer of the brown/orange muck. To be honest it’s been this way for the past year. It’s just been one of those “out of sight, out of mind” things besides checking that it’s full and not oil contaminated.