Avis is not the only hire company to install transponders in their cars to deal with the toll charges on the Algarve motorway (A22). They were beaten to it earlier this year by a small local company in Lagos called Lagorent. Not only that but Lagorent charges a flat five euros for the service of providing the transponder against Avis' 1.84 euros per day. I won't go into all the other benefits of choosing them, but they have a website and bookings can be made through their English Agents (Economy Car Hire) so it easy to compare them against each other. I have no axe to grind on behalf of any of the hire companies but we have been holidaying in the Algarve for 25 years and have experienced most of the hire companies, and have found that the big name hirers are not always the best.