What could be wrong with my coolant system

Hello, it's very hard to know what is "safe" -- if your coolant reservoir is low or empty, the coolant must be going somewhere. It is either leaking internally inside the engine or externally which should be visible. In either case, cooling system issues are serious, and need to be resolved sooner than later. If you have an internal engine coolant leak, further performance issues will occur and internal damage could occur. If you have an external leak, overheating can eventually occur, causing damage. I would have this inspected and diagnosed sooner than later.

I don't see a location posted - be very careful adding *water* to the cooling system if in a cold climate!