Cross Country Car Rental?

Howdy AMIGOS!

I'm looking to rent a car for a cross-country trip, picking up and returning it in Madrid. My plan is to drive around Spain and Portugal for about two weeks before returning the car to Madrid.

I'm specifically looking for car rental recommendations with low or no cross-border fees for travel between Spain and Portugal.

I've searched on Google, ChatGPT, and contacted the support teams of major rental companies, but haven't found a clear answer. Do you have any or recommendations?

Cheers!