I understand it is a difficult trip by train, but how are the roads? I will have a rental car and prefer to go by way of Lyon. Perhaps stopping in that city for a meal. Thank you.
The roads are excellent, mostly highways for that 6-hour drive. And there's no other way to go, really.
You'll probably need the car to visit the Sarlat area, so you might as well rent it before you arrive in the area, and keep it after. Depending on where you're coming from, it would make sense to pick up the car in Limoges, Brive or Bordeaux.
As for a lunch stop in Lyon, I would argue against it because it is a large city, so you would lose a lot of time navigating, parking, etc. It would also require that you leave Sarlat quite early. It's not a hard NO for me, though.
My alternative suggestion for lunch is Thiers, a pretty small town between Clermont and Lyon.
Now, maybe we can give even better advice if you give us your broader itinerary? Perhaps some things can be rearranged to avoid this cross country journey.
CDG to Gourdon by train on 5 September; to Daglan and Sarlat until the 13th. May want to go to Pech Merle/Cahors and possibly Carcassonne. Need to drop off car in Sarlat on 17 September and train back to CDG on 18th. Maybe hold off on Annecy until next trip?
So you'd only have between the 13th and the 17th to go from Sarlat towards Annecy and back?
If you can change your car reservation to do a drop off in Annecy, then it's fine, otherwise, it's a lot of driving.
Alternative suggestions:
- If you are going towards Carcassonne, you could turn this into a loop and drive from Carcassonne to Annecy, then either leave the car there or go back to Sarlat. Carcassonne to Annecy is also 6 hours or thereabouts.
- Drop Annecy this time, but get a "mountain fix" by spending some time further south from Carcassonne towards the Pyrénées and visit a few Cathar sites (old castles perched on mountains).
Annecy or no Annecy, I'm also really not sure that Sarlat is a convenient place to drop off the car to go back to CDG, given the lack of good public transportation in the area, but if everything is set in stone already, there's always a way back to Paris.