No, I'm not losing coolant. When I first bought the car it was low on coolant and so I topped up. The it was fine. This time, I changed the thermostat, and I lost more than I expected during that process. I had a litre of coolant in the back of my car and so I used that to top back up, but I must have lost more than a litre during the stat change. So I will have to top it up again today until it stabilizes. I'm happy enough that the coolant isn't leaking out anywhere. So the temperature gauge is the only issue in relation to cooling. I now suspect the temperature sensor. I suppose swapping that out is going to lose some coolant also! So there could be more topping up before this is finished!!!