wah, got such thing as rain more heavy will wash cleaner meh?!!
in short, rain water in sg is acidic. it'll strip the car of its
wax and in the absence of wax, the lacquer on the paintwork itself
to the point the paint itself is exposed to the elements. by which
time, no amount of polishing will bring the shine back into the
paint.
i wash the car once a week and in between, i make it a point to
wipe the top portion of the car every few days to keep water spots
at bay. apparently, it's not good enough 
