Before completing this modification to your vehicle, be sure to check local laws, as it can be an illegal combination in many states...
Oregon says that fog lights are to be used as follows:
"Fog lights are designed to be used at low speeds in fog, heavy mist, snow and other situations where visibility is significantly reduced. Front fog lights are generally aimed and mounted low to increase the illumination directed towards the road surface. In low visibility situations, fog lights should be turned off when an oncoming vehicle approaches. In normal visibility conditions, fog or auxiliary lights should be turned off.
According to Oregon law, fog and/or auxiliary lights must be used like the high beam headlight system of your car. They must be turned off within 500 feet of approaching an oncoming vehicle and 350 feet when following another vehicle. The color of fog and/or auxiliary lights is also regulated. Fog lights may be either white or amber (yellow). Rules prohibit other colors such as blue."
If that doesn't convince you to at least check, remember that it is a Class B traffic violation and you can be ticketed by the nice Law Enforcement Officers...
ORS 811.520 Unlawful use or failure to use lights. Class B traffic violation.
Be careful out there