We are considering renting a car in Porto and driving to Granada and other southern Spain destinations. Is it a problem to rent a car in Portugal and then drop off in Spain? Another plan would be to fly from Porto to Seville and rent a car there to explore the region.
I imagine you can find a car-rental agency that will allow you to drop a Portuguese car in Spain, but you will 99% for certain pay a great deal of money for the privilege of doing that. The Portuguese car cannot be rented in Spain, so the company will have to send someone to fetch it and drive it back to Portugal. If you want more specifics, you might contact the one or more of the car-rental consolidators (AutoEurope, Kemwel and Gemut).
I think flying to Seville is a much better idea. I don't like mid-trip flights, but the ground connections between Portugal and Spain are few.
Agree. Fly between Porto and Sevilla. The drop off charges are crazy. Plus, it’s a very long drive with lots of tolls - at least In Portugal. With the inexpensive flights you can likely get - it might even be cheaper to fly.