It is, in a sense, oil - traffic/oil film, smoke emission from vehicle, etc. Something like how your skin would feel and look when wiping with a tissue paper after a few hours walking around in the middle of KL. You should be able to easily remove it with a light polish or an All-In-One (AIO) like Duragloss 501, 3M One Step Cleaner Wax, Meguairs Ultimate Polish or the like. You can also strip it with a 'chemical wash' using a mild all purpose cleaner, but just remember to wax your car again afterwards.
I guess a white car also. See above.
hhrrmmm.....define reasonable please... ?