Mercedes starting hooking up the rear foglights for Canadian cars sometime around 1991-1992 or so. I use mine in fog, and people tend to form a line behind me, as the light works VERY well.
The lower bumper foglights that you see on so many E30 and E36 BMW models seem to not work in fog, but the rest of the time, only. The drivers seem to be saying to us "See, I am a highly skilled European driver" but they are really coming across as "I am a moron that's trying to look cool."
Use your fog lights in the fog.
1998 C230 "Black Betty"