I've purchased nine or ten new cars for myself and my wife over the last 30 years, and the only ones that I've had problems with were ones that had been used as demo vehicles at the dealers. Coincidence? Maybe, but I always insist now on getting a new car "right off the truck." Most dealers are willing to oblige if you make it clear that refusing to do so means losing the sale. Of course, that can mean waiting a while to get the model and color you want, but I have found it worthwhile.