Unless the fog lights are aimed correctly about the only thing they do
it to light up the area directly in front of the car that the
headlights don't illuminate. Factory or dealer installed fog lights
act more as a cosmetic function than improve visibility. The reason
it is so difficult to drive in fog, it that the light is reflected
back off of the small water droplets, and even the low beams cause
this reflection. If you install them yourself, it is possible to be
able to turn them on and off independent of the main lighting and with
proper aiming they will definitely help, but if the dealer installs
them, they will be wired to come on with your headlights basically
defeating their purpose.
================================================The only time I wished I had fog lights was off-road, trying to get off a
mountain top one night. I couldn't see anything but fog when the headlights
were on and the parking lights were too dim. I had to scout on foot for
twenty feet or so at a time because I couldn't see the sides of the road.
They would have been worthless if they required the headlights to be on - I
would have had to unplug the headlights.