All the peps working as mechanic will tell you that they are not surprised by what you might say or what you say. Basically we have seen nearly everything some users can do to their cars. The first story that comes up to my head is this one :

We got a VW Polo back on our garage on a truck because the car was "not working" anymore. I opened the engine bay, and saw dry water liquid everywhere, the engine water bottle MELTED, yes you red right, it had MELTED. Then I looked at the engine, and the inlet manifold (which was made from plastic) had melted too on the head due to heat. In fact the water warning light was working inside the car, but the woman thought it was just a "service light" telling her it was time to service the car.

She drove 50km like that (can't believe the engine survived that) before it died. Can't remember what was exactly the cause why the engine overheated but lot of damages just because some people should just not be able to drive cars. And it wasn't a new car, she had it for few years.