Park outside Paris and get a train into the city

It might be a bad idea.

The A4 is a pretty easy freeway that becomes the Quai de Bercy (somewhere at about the peripherique) and shoots down the right bank of the Seine. At the Bercy Bridge, it changes names to Quai de Rapee. The next bridge is the de Gaulle -- don't turn left to cross it, hook a right onto Rue Van Gogh, then the next right onto R. Bercy. The Gare de Lyon is on your left, a huge parking garage on your right. The whole deal from Rheims is two right turns and all but a couple of blocks on four lanes or better. No cross-traffic turns, all turns with stop lights, and only four names to remember. G Lyon has four metro/rer lines running through it.

There was a similar discussion about a year ago with contributors chunking junk they'd glommed of the internet and a couple of people who'd done really dumb things to achieve the end that you're shooting for. I've been dorking about Paris longer than most people have been alive and driving it for close to fifty years. I obviously didn't recognize every area, but knew where most of them were and it gave me the acute willys just thinking about it. You'll want to read the rental agreement very carefully about where you can abandon a car without liability.

It only takes 45 minutes by train...city center to city center. Are you sure you REALLY need to drive???

I was holding back and only sort of answering the specific question, but my first thought was the same as Tim's.

Assuming he's right on the train time, it's an hour and a half drive. The train probably costs a bit more for two people.

Here's where you need to get out the stubby pencil.

Gas is going to be about twenty bucks, tolls around fifteen. Figure twenty-five or so per day for parking.

Bounce this against the train cost, and (if you're going to do mored driving after Paris) the cost of two maybe short-term rentals against a cheaper daily rate if you kept one car the whole time.

Also, if my previous idea sticks in you craw, add in the cost and time of getting back to some intermediate point where you left the car.

I had my rental car from Germany when I arrived in Rheims, but did not want to take the car to Paris... so I just found a hotel in Rheims, stayed the one night we wanted to visit the city, then the next day took the train to Paris and left our car at the hotel parking lot. It was so much easier and cheaper (about 8 euro per nite) We then returned to Rheims and picked up our car for the remainder of our trip. The 2 week rental rate made this cheaper than getting a new car as we were only 2 nites in Paris on this trip.