
As a general rule, you can utilize public transportation in many countries, and explore a large percentage of the country. This mode of transport brings you into the culture quickly. But there are times when certain locations are much too difficult except via car.
Having driven a lot in Europe and as easy going as the Portuguese are, they do love to drive fast. Not crazy and always respectful, unlike other countries. And be aware, they stop for pedestrians! This is also unlike a few countries I’ve driven.
First I checked with my credit card company to see what coverage was offered or not. Then I checked out the agencies the card was touting. Sometimes there are deals, double points, etc. I know of several European companies in addition to our standard US options (which also can be found throughout Western Europe). If you have a preference, stick to them. I don’t.

So I used EuropCar in Portugal. They offer an array of vehicles, from super efficient (about roller skate size) to SUV. Parking can be difficult and tight (you better be very good at parallel parking!) and many places you must feed the meter, or you will get a ticket. Thus my choice in vehicle.
I rented a Fiat500 for a week and since part of my insurance was covered on my card, I ordered the basic coverage. I also ordered a VVR e-reader for the car. This allows me to use the toll roads and drive through the “V” lanes. It auto charges onto my credit card. Simple. And the per day cost is €1,40. So my total cost for the week was €67. It was on me to return the car full of petrol. And by the time we drove several hundred km, I spent €60 and returned the car full.

EuroCar charges a €300 hold on your card. But upon return (with no issues), it was immediately released. So my cost for the week was €127 ($141). We stayed off the toll roads for the majority.
So I could have saved €9,80 by not including the VVR. But I did need to use the toll road when I returned my car. So it was worth it to me.