In my recent experience, the car rental companies have gotten rid of just about all of their diesel cars. I haven't had one in at least 2 years. The share of diesel in new French (private) cars has dropped from something like 75% to about 33% in just two years as well. And diesel fuel is no longer cheaper than unleaded.

The drop is not really surprising since the big cities of Europe are planning a total ban of diesel vehicles as of 2025 or 2030.

That has been my experience too.