After all the discussions, I would like to tell that at heavy rains I hardly can't see any thing in the rear its due to rain and the water splashing out from the tires at high speeds (the glass would be dusty) as I don't have an defogger or an A/C I opted for an rear wiper and it was also for style & now in search of an defogger.
Is it worth fitting an rear wiper on M800 (Because I have seen no one did it)?