A cooling fluid pump was replaced before the coolant leak appeared.
The engine had sufficient oil.
There's an analog gauge for oil temperature, it has a black zone and a small red zone at the top. It did not touch the red zone, but it came close.
There's no cooling fluid gauge. There's a warning light for the engine. I saw that when the engine stopped.
Also, heating was on full but it didn't work at that trip, it was freezing outside.
Radiator cooling fluid (green) apparently leaked from a tube fitted somewhere between radiator and engine. It was visible from beneath the car for the mechanic. I haven't seen it myself though. After the engine had stopped, cooling fluid was added and the car started again, I drove the car to the shop to repair the leakage. Heating worked right away.