Ok so I'm on my way to Europe for the first time the end of June and will be leaving beginning of July. We will have about 17 days of sightseeing. I found a car leasing company that can get us a diesel station wagon that gets about 50mpg for around $1600usd. This seems really reasonable to me, tell me if I'm wrong. My main concern is the drive from Paris to Madrid which I know is about 12 hours long. I have given myself about three days to drive this as it seems a great way to experience some of the French and Spanish countryside. Does anyone have any suggestions to where I absolutely need to stop? I think I want to check out Normandy, the Loire Valley and Bordeaux. Like I said this is my first trip and am looking for some advice.
You could easily spend a week or longer on that run. But first things first....Normandy will be out of your way if you're driving Paris-Madrid. Besides the other destinations you've listed, I wouldn't leave out Carcassonne in southern France, then cutting back over to travel through the Basque lands of Spain...San Sebastian, Bilbao, and Zaragoza...before heading to Madrid.
3 days is hardly enough time to explore those destinations. Perhaps you could pick one area to stop and stay for two nights? And as the other poster noted, Normandy is off of your main line of travel.