I use a Karacher to wash my old F31. Albeit towards the end I did notice the clear coat on the front bumper was flaking off when sprayed with the jet wash! The car was 10 years old...
Generally though I would go easy on the pressure by adjusting the jet spray's nozzle. I'm a big fan of contact-free washing using my foam spray attachment. Don't believe the youTube vids which claim the dirt will just wash off, I guess it depends on how dirty you car is and if it had been previously waxed etc., will have a bearing of how easy it is to wash off any dirt or grime.
First pass with the Karacher to wet the car down and remove loose dirt.
Second pass with foam attachment - leave for 5 minutes for foam to fall away.
Third pass with Karacher again.
Then take the car for a spin to air-dry...
