Loosing water after a 40 mile highway drive than bumper to bumper traffic for 20 minutes. Other wise can drive 40 miles,stop drive 10miles city than 40 miles highway. No water loss.
My car has 235000 miles.
My car has an automatic transmission.
Any kind of water loss is usually not good. You cars performance completely depends on the cooling system. Your vehicle gets too hot, and the engine is destroyed. Do not run the vehicle out of coolant. There is not enough information to accurately tell you what the issue is. How much coolant is being lost on the trip total? Does the leak seem to be worse at lower engine speeds? Have you done a visual inspection with the car running in idle? If you do not see a leak, there is a possibility the engine could be consuming it. Have you checked the oil for water? Has the vehicle appeared to get above normal operating temperature? A coolant leak can come from a bad hose, the radiator, the engine, the water pump, and several other components. I suggest starting with a visual inspection and seeing if you can spot where the leak is coming from.