The aerodynamics on the Jazz seem to cause a lot of dirt on the tailgate - more than other cars I’ve had.
This was after only a couple of motorway trips over the last few days - other cars on the road weren’t as dirty:
There is also quite a bit of buildup on the sides, but thankfully the aerodynamics mean it stops below the window line:
The front also gets a lot of dirt - something I’d noticed in the summer with the number of flies.
A lot of the dirt is around where the front grill is on the crosstar, so the ‘blanking plate’ grill on the standard jazz does seem to be for the aerodynamics: