I want to be able to select in one search both
GMC and Cadillac, a couple different models
of each, having GM factory certified vehicles
only and several different zip codes near
Philadelphia, Chicago and Detroit. Van I do
You don't want much do you? You will need to do different searches for each make and city (at least 6 total). Pick a zip code and a search radius that is big enough to cover the areas you want.