Diesel or Gas

Gas stations will all have both types of fuel.
I am surprised they charge so much more for renting a diesel. I doubt you will make up the $300 difference in one month. You would need to travel thousands of km during your vacation. That is not likely.

Thanks. Gas it is.

Why don't you look into leasing a car from the manufacturer for the month? AutoEurope.com has prices listed, and they're substantially lower than your rental quoted. Diesel vehicles are also less expensive, and I've found them to perform very well and getting over 50 mpg.
There are other benefits to leasing like full coverage insurance is included, you can take the car anywhere including places rental companies prohibit and you don't have to pay for additional drivers.
You can pick lease cars up in most larger French cities, but I looked at Bordeaux that is relatively close to Sariat by train.

I will be leasing. That's what I've done the last 4 or so trips. You can pick out exactly what you want and the cost is generally better. I will probably lease thru Renault USA. I've rented in the past from AutoEurope but for leasing I'd rather go direct. One small worry some thing in the AutoEurope lease is a note that says if you're over 65 they reserve the right to up the cost when you get there.

We will be flying into and out of Toulouse and that is one of the car pickup places.

There used to be a large gap in fuel prices in France, with diesel being much cheaper, but this is no longer the case. Fuel at supermarkets is significantly cheaper than at a standard petrol station.

Fuel economy varies significantly depending on the car chosen. I have an automatic 2 litre diesel VW estate car that averages about 62 mpg on motorway drives and nearer 30 in town. I also have a small manual Skoda Citigo petrol engine that averages 72 on a long motorway journey and 40 in town. Depending on the emissions, you maybe more limited where you can drive a diesel car in France.

Diesel, unleaded and LPG are all widely available.

in the past I have seen articles that say the cost break-over point is about 2500 miles, I lave leased six diesel cars with automatic transmissions over the years, I do not drive for fuel economy, I just drive with traffic and the worst overall fuel economy I got for an entire trip was just a bit over 44 mpg. The cars run very well and diesel smell is a thing of the distant past. The only concern I have right now is the issues that the VW emission cheating problem has created. Last year I picked up our car in Frankfurt and it took about fifteen minutes to get the new certification sticker.

Since we re retired and our trips are at least three weeks, we lease. The car is brand new and is what you reserved, not what they have on the lot and there are no surprise charges when you pick it up as you have prepaid the whole thing. For me this is critical since my wife does not do manual transmissions. The car will be insured to the hilt, additional drivers are free and the only age requirement is that you are over eighteen. Renault USA does Renault an AutoFrance does Peugeot. To do a lease you need to deal with French manufacturers since the whole program exists due to a loop hole on the French VAT law.

the whole program exists due to a loop hole on the French VAT law.

Is that true, or is it intentional? I know it's been going on for a long time, since I leased a car in France over 20 years ago.

You might find this link to mon-essence.fr handy.

Thanks. I'll use that!

In July we leased a CITROEN car in the model we wanted and lower priced gas version. About a month later, received email that we had been upgraded to a diesel at no extra charge.

We’ve had the same happen with car rentals. Not worth paying extra for diesel car.

Thanks for all the advice folks. I appreciate it. Will be leasing a Renault, gas version, for a month, mid May to mid June. Looking forward to getting back to Perigord.

Regarding availability of diesel fuel: nearly half of Europe’s car fleet run on diesel, so all gas station have both petrol (gas) and diesel fuel.