I seem to be loosing water over a long period of time. I have checked all the pipes/engine for leaks it's not dripping on the road it seems to be evaporating after a few trips
Also on the motorway the faster i go the more the car temp goes up at about 80mph the needle goes just below red, but when i drop to 65/70mph it comes down to half

ps. oil and water are NOT mixing

i would appreciate any help/advice

Thanks